Merge #15277: contrib: Enable building in Guix containers

751549b52a9a4cd27389d807ae67f02bbb39cd7f contrib: guix: Additional clarifications re: substitutes (Carl Dong)
cd3e947f50db7cfe05c05b368c25742193729a62 contrib: guix: Various improvements. (Carl Dong)
8dff3e48a9e03299468ed3b342642f01f70da9db contrib: guix: Clarify SOURCE_DATE_EPOCH. (Carl Dong)
3e80ec3ea9691c7c89173de922a113e643fe976b contrib: Add deterministic Guix builds. (Carl Dong)

Pull request description:

  ~~**This post is kept updated as this project progresses. Use this [latest update link](https://github.com/bitcoin/bitcoin/pull/15277#issuecomment-497303718) to see what's new.**~~

  Please read the `README.md`.

  -----

  ### Guix Introduction

  This PR enables building bitcoin in Guix containers. [Guix](https://www.gnu.org/software/guix/manual/en/html_node/Features.html) is a transactional package manager much like Nix, but unlike Nix, it has more of a focus on [bootstrappability](https://www.gnu.org/software/guix/manual/en/html_node/Bootstrapping.html) and [reproducibility](https://www.gnu.org/software/guix/blog/tags/reproducible-builds/) which are attractive for security-sensitive projects like bitcoin.

  ### Guix Build Walkthrough

  Please read the `README.md`.

  [Old instructions no. 4](https://github.com/bitcoin/bitcoin/pull/15277#issuecomment-497303718)

  [Old instructions no. 3](https://github.com/bitcoin/bitcoin/pull/15277#issuecomment-493827011)

  [Old instructions no. 2](https://github.com/bitcoin/bitcoin/pull/15277#issuecomment-471658439)

  <details>
  <summary>Old instructions no. 1</summary>
  In this PR, we define a Guix [manifest](https://www.gnu.org/software/guix/manual/en/html_node/Invoking-guix-package.html#profile_002dmanifest) in `contrib/guix/manifest.scm`, which declares what packages we want in our environment.

  We can then invoke
  ```
  guix environment --manifest=contrib/guix/manifest.scm --container --pure --no-grafts --no-substitutes
  ```
  To have Guix:
  1. Build an environment containing the packages we defined in our `contrib/guix/manifest.scm` manifest from the Guix bootstrap binaries (see [bootstrappability](https://www.gnu.org/software/guix/manual/en/html_node/Bootstrapping.html) for more details).
  2. Start a container with that environment that has no network access, and no access to the host's filesystem except to the `pwd` that it was started in.
  3. Drop you into a shell in that container.

  > Note: if you don't want to wait hours for Guix to build the entire world from scratch, you can eliminate the `--no-substitutes` option to have Guix download from available binary sources. Note that this convenience doesn't necessarily compromise your security, as you can check that a package was built correctly after the fact using `guix build --check <packagename>`

  Therefore, we can perform a build of bitcoin much like in Gitian by invoking the following:

  ```
  make -C depends -j"$(nproc)" download && \
      cat contrib/guix/build.sh | guix environment --manifest=contrib/guix/manifest.scm --container --pure --no-grafts --no-substitutes
  ```

  We don't include `make -C depends -j"$(nproc)" download` inside `contrib/guix/build.sh` because `contrib/guix/build.sh` is run inside the container, which has no network access (which is a good thing).
  </details>

  ### Rationale

  I believe that this represents a substantial improvement for the "supply chain security" of bitcoin because:

  1. We no longer have to rely on Ubuntu for our build environment for our releases ([oh the horror](https://github.com/bitcoin/bitcoin/blob/72bd4ab867e3be0d8410403d9641c08288d343e3/contrib/gitian-descriptors/gitian-linux.yml#L10)), because Guix builds everything about the container, we can perform this on almost any Linux distro/system.
  2. It is now much easier to determine what trusted binaries are in our supply chain, and even make a nice visualization! (see [bootstrappability](https://www.gnu.org/software/guix/manual/en/html_node/Bootstrapping.html)).
  3. There is active effort among Guix folks to minimize the number of trusted binaries even further. OriansJ's [stage0](https://github.com/oriansj/stage0), and janneke's [Mes](https://www.gnu.org/software/mes/) all aim to achieve [reduced binary boostrap](http://joyofsource.com/reduced-binary-seed-bootstrap.html) for Guix. In fact, I believe if OriansJ gets his way, we will end up some day with only a single trusted binary: hex0 (a ~500 byte self-hosting hex assembler).

  ### Steps to Completion

  - [x] Successfully build bitcoin inside the Guix environment
  - [x] Make `check-symbols` pass
  - [x] Do the above but without nasty hacks
  - [x] Solve some of the more innocuous hacks
  - [ ] Make it cross-compile (HELP WANTED HERE)
    - [x] Linux
      - [x] x86_64-linux-gnu
      - [x] i686-linux-gnu
      - [x] aarch64-linux-gnu
      - [x] arm-linux-gnueabihf
      - [x] riscv64-linux-gnu
    - [ ] OS X
      - [ ] x86_64-apple-darwin14
    - [ ] Windows
      - [ ] x86_64-w64-mingw32
  - [ ] Maybe make importer for depends syntax
  - [ ] Document build process for future releases
  - [ ] Extra: Pin the revision of Guix that we build with with Guix [inferiors](https://www.gnu.org/software/guix/manual/en/html_node/Inferiors.html)

  ### Help Wanted

  [Old content no. 3](https://github.com/bitcoin/bitcoin/pull/15277#issuecomment-483318210)

  [Old content no. 2](https://github.com/bitcoin/bitcoin/pull/15277#issuecomment-471658439)

  <details>
  <summary>Old content no. 1</summary>
  As of now, the command described above to perform a build of bitcoin a lot like Gitian works, but fails at the `check-symbols` stage. This is because a few dynamic libraries are linked in that shouldn't be.

  Here's what `ldd src/bitcoind` looks like when built in a Guix container:
  ```
  	linux-vdso.so.1 (0x00007ffcc2d90000)
  	libdl.so.2 => /gnu/store/h90vnqw0nwd0hhm1l5dgxsdrigddfmq4-glibc-2.28/lib/libdl.so.2 (0x00007fb7eda09000)
  	librt.so.1 => /gnu/store/h90vnqw0nwd0hhm1l5dgxsdrigddfmq4-glibc-2.28/lib/librt.so.1 (0x00007fb7ed9ff000)
  	libstdc++.so.6 => /gnu/store/4sqps8dczv3g7rwbdibfz6rf5jlk7w90-gcc-5.5.0-lib/lib/libstdc++.so.6 (0x00007fb7ed87c000)
  	libpthread.so.0 => /gnu/store/h90vnqw0nwd0hhm1l5dgxsdrigddfmq4-glibc-2.28/lib/libpthread.so.0 (0x00007fb7ed85b000)
  	libm.so.6 => /gnu/store/h90vnqw0nwd0hhm1l5dgxsdrigddfmq4-glibc-2.28/lib/libm.so.6 (0x00007fb7ed6da000)
  	libgcc_s.so.1 => /gnu/store/4sqps8dczv3g7rwbdibfz6rf5jlk7w90-gcc-5.5.0-lib/lib/libgcc_s.so.1 (0x00007fb7ed6bf000)
  	libc.so.6 => /gnu/store/h90vnqw0nwd0hhm1l5dgxsdrigddfmq4-glibc-2.28/lib/libc.so.6 (0x00007fb7ed506000)
  	/gnu/store/h90vnqw0nwd0hhm1l5dgxsdrigddfmq4-glibc-2.28/lib/ld-linux-x86-64.so.2 => /usr/lib64/ld-linux-x86-64.so.2 (0x00007fb7ee3a0000)
  ```

  And here's what it looks in one of our releases:
  ```
  	linux-vdso.so.1 (0x00007ffff52cd000)
  	libpthread.so.0 => /usr/lib/libpthread.so.0 (0x00007f87726b4000)
  	librt.so.1 => /usr/lib/librt.so.1 (0x00007f87726aa000)
  	libm.so.6 => /usr/lib/libm.so.6 (0x00007f8772525000)
  	libgcc_s.so.1 => /usr/lib/libgcc_s.so.1 (0x00007f877250b000)
  	libc.so.6 => /usr/lib/libc.so.6 (0x00007f8772347000)
  	/lib64/ld-linux-x86-64.so.2 => /usr/lib64/ld-linux-x86-64.so.2 (0x00007f8773392000)
  ```

  ~~I suspect it is because my script does not apply the gitian-input patches [described in the release process](https://github.com/bitcoin/bitcoin/blob/master/doc/release-process.md#fetch-and-create-inputs-first-time-or-when-dependency-versions-change) but there is no description as to how these patches are applied.~~ It might also be something else entirely.

  Edit: It is something else. It appears that the gitian inputs are only used by [`gitian-win-signer.yml`](https://github.com/bitcoin/bitcoin/blob/d6e700e40f861ddd6743f4d13f0d6f6bc19093c2/contrib/gitian-descriptors/gitian-win-signer.yml#L14)
  </details>

  ### How to Help

  1. Install Guix on your distro either [from source](https://www.gnu.org/software/guix/manual/en/html_node/Requirements.html) or perform a [binary installation](https://www.gnu.org/software/guix/manual/en/html_node/Binary-Installation.html#Binary-Installation)
  2. Try out my branch and the command described above!

ACKs for top commit:
  MarcoFalke:
    Thanks for the replies. ACK 751549b52a9a4cd27389d807ae67f02bbb39cd7f
  laanwj:
    ACK 751549b52a9a4cd27389d807ae67f02bbb39cd7f

Tree-SHA512: 50e6ab58c6bda9a67125b6271daf7eff0ca57d0efa8941ed3cd951e5bf78b31552fc5e537b1e1bcf2d3cc918c63adf19d685aa117a0f851024dc67e697890a8d

5 files changed, 634 insertions, 1 deletions

diff --git a/contrib/guix/README.md b/contrib/guix/README.md
new file mode 100644
index 0000000000..4dfa1729a5
--- /dev/null
+++ b/contrib/guix/README.md
@@ -0,0 +1,229 @@
+# Bootstrappable Bitcoin Core Builds
+
+This directory contains the files necessary to perform bootstrappable Bitcoin
+Core builds.
+
+[Bootstrappability][b17e] furthers our binary security guarantees by allowing us
+to _audit and reproduce_ our toolchain instead of blindly _trusting_ binary
+downloads.
+
+We achieve bootstrappability by using Guix as a functional package manager.
+
+## Requirements
+
+Conservatively, a x86_64 machine with:
+
+- 2 or more logical cores
+- 4GB of free disk space on the partition that /gnu/store will reside in
+- 24GB of free disk space on the partition that the Bitcoin Core git repository
+  resides in
+
+> Note: these requirements are slightly less onerous than those of Gitian builds
+
+## Setup
+
+### Installing Guix
+
+If you're just testing this out, you can use the
+[Dockerfile][fanquake/guix-docker] for convenience. It automatically speeds up
+your builds by [using substitutes](#speeding-up-builds-with-substitute-servers).
+If you don't want this behaviour, refer to the [next
+section](#choosing-your-security-model).
+
+Otherwise, follow the [Guix installation guide][guix/bin-install].
+
+> Note: For those who like to keep their filesystems clean, Guix is designed to
+> be very standalone and _will not_ conflict with your system's package
+> manager/existing setup. It _only_ touches `/var/guix`, `/gnu`, and
+> `~/.config/guix`.
+
+### Choosing your security model
+
+Guix allows us to achieve better binary security by using our CPU time to build
+everything from scratch. However, it doesn't sacrifice user choice in pursuit of
+this: users can decide whether or not to bootstrap and to use substitutes.
+
+After installation, you may want to consider [adding substitute
+servers](#speeding-up-builds-with-substitute-servers) to speed up your build if
+that fits your security model (say, if you're just testing that this works).
+This is skippable if you're using the [Dockerfile][fanquake/guix-docker].
+
+If you prefer not to use any substitutes, make sure to set
+`ADDITIONAL_GUIX_ENVIRONMENT_FLAGS` like the following snippet. The first build
+will take a while, but the resulting packages will be cached for future builds.
+
+```sh
+export ADDITIONAL_GUIX_ENVIRONMENT_FLAGS='--no-substitutes'
+```
+
+Likewise, to perform a bootstrapped build (takes even longer):
+
+```sh
+export ADDITIONAL_GUIX_ENVIRONMENT_FLAGS='--bootstrap --no-substitutes'
+```
+
+### Using the right Guix
+
+Once Guix is installed, deploy our patched version into your current Guix
+profile. The changes there are slowly being upstreamed.
+
+```sh
+guix pull --url=https://github.com/dongcarl/guix.git \
+          --commit=82c77e52b8b46e0a3aad2cb12307c2e30547deec \
+          --max-jobs=4 # change accordingly
+```
+
+Make sure that you are using your current profile. (You are prompted to do this
+at the end of the `guix pull`)
+
+```bash
+export PATH="${HOME}/.config/guix/current/bin${PATH:+:}$PATH"
+```
+
+> Note: There is ongoing work to eliminate this entire section using Guix
+> [inferiors][guix/inferiors] and [channels][guix/channels].
+
+## Usage
+
+### As a Development Environment
+
+For a Bitcoin Core depends development environment, simply invoke
+
+```sh
+guix environment --manifest=contrib/guix/manifest.scm
+```
+
+And you'll land back in your shell with all the build dependencies required for
+a `depends` build injected into your environment.
+
+### As a Tool for Deterministic Builds
+
+From the top of a clean Bitcoin Core repository:
+
+```sh
+./contrib/guix/guix-build.sh
+```
+
+After the build finishes successfully (check the status code please), compare
+hashes:
+
+```sh
+find output/ -type f -print0 | sort -z | xargs -r0 sha256sum
+```
+
+#### Recognized environment variables
+
+* _**HOSTS**_
+
+  Override the space-separated list of platform triples for which to perform a
+  bootstrappable build. _(defaults to "i686-linux-gnu x86\_64-linux-gnu
+  arm-linux-gnueabihf aarch64-linux-gnu riscv64-linux-gnu")_
+
+  > Windows and OS X platform triplet support are WIP.
+
+* _**SOURCES_PATH**_
+
+  Set the depends tree download cache for sources. This is passed through to the
+  depends tree. Setting this to the same directory across multiple builds of the
+  depends tree can eliminate unnecessary redownloading of package sources.
+
+* _**MAX_JOBS**_
+
+  Override the maximum number of jobs to run simultaneously, you might want to
+  do so on a memory-limited machine. This may be passed to `make` as in `make
+  --jobs="$MAX_JOBS"` or `xargs` as in `xargs -P"$MAX_JOBS"`. _(defaults to the
+  value of `nproc` outside the container)_
+
+* _**SOURCE_DATE_EPOCH**_
+
+  Override the reference UNIX timestamp used for bit-for-bit reproducibility,
+  the variable name conforms to [standard][r12e/source-date-epoch]. _(defaults
+  to the output of `$(git log --format=%at -1)`)_
+
+* _**V**_
+
+  If non-empty, will pass `V=1` to all `make` invocations, making `make` output
+  verbose.
+
+* _**ADDITIONAL_GUIX_ENVIRONMENT_FLAGS**_
+
+  Additional flags to be passed to `guix environment`. For a fully-bootstrapped
+  build, set this to `--bootstrap --no-substitutes` (refer to the [security
+  model section](#choosing-your-security-model) for more details). Note that a
+  fully-bootstrapped build will take quite a long time on the first run.
+
+## Tips and Tricks
+
+### Speeding up builds with substitute servers
+
+_This whole section is automatically done in the convenience
+[Dockerfiles][fanquake/guix-docker]_
+
+For those who are used to life in the fast _(and trustful)_ lane, you can use
+[substitute servers][guix/substitutes] to enable binary downloads of packages.
+
+> For those who only want to use substitutes from the official Guix build farm
+> and have authorized the build farm's signing key during Guix's installation,
+> you don't need to do anything.
+
+#### Authorize the signing keys
+
+For the official Guix build farm at https://ci.guix.gnu.org, run as root:
+
+```
+guix archive --authorize < ~root/.config/guix/current/share/guix/ci.guix.gnu.org.pub
+```
+
+For dongcarl's substitute server at https://guix.carldong.io, run as root:
+
+```sh
+wget -qO- 'https://guix.carldong.io/signing-key.pub' | guix archive --authorize
+```
+
+#### Use the substitute servers
+
+The official Guix build farm at https://ci.guix.gnu.org is automatically used
+unless the `--no-substitutes` flag is supplied.
+
+This can be overridden for all `guix` invocations by passing the
+`--substitute-urls` option to your invocation of `guix-daemon`. This can also be
+overridden on a call-by-call basis by passing the same `--substitute-urls`
+option to client tools such at `guix environment`.
+
+To use dongcarl's substitute server for Bitcoin Core builds after having
+[authorized his signing key](#authorize-the-signing-keys):
+
+```
+export ADDITIONAL_GUIX_ENVIRONMENT_FLAGS='--substitute-urls="https://guix.carldong.io https://ci.guix.gnu.org"'
+```
+
+## FAQ
+
+### How can I trust the binary installation?
+
+As mentioned at the bottom of [this manual page][guix/bin-install]:
+
+> The binary installation tarballs can be (re)produced and verified simply by
+> running the following command in the Guix source tree:
+>
+>     make guix-binary.x86_64-linux.tar.xz
+
+### When will Guix be packaged in debian?
+
+Vagrant Cascadian has been making good progress on this
+[here][debian/guix-package]. We have all the pieces needed to put up an APT
+repository and will likely put one up soon.
+
+[b17e]: http://bootstrappable.org/
+[r12e/source-date-epoch]: https://reproducible-builds.org/docs/source-date-epoch/
+
+[guix/install.sh]: https://git.savannah.gnu.org/cgit/guix.git/plain/etc/guix-install.sh
+[guix/bin-install]: https://www.gnu.org/software/guix/manual/en/html_node/Binary-Installation.html
+[guix/env-setup]: https://www.gnu.org/software/guix/manual/en/html_node/Build-Environment-Setup.html
+[guix/substitutes]: https://www.gnu.org/software/guix/manual/en/html_node/Substitutes.html
+[guix/substitute-server-auth]: https://www.gnu.org/software/guix/manual/en/html_node/Substitute-Server-Authorization.html
+[guix/inferiors]: https://www.gnu.org/software/guix/manual/en/html_node/Inferiors.html
+[guix/channels]: https://www.gnu.org/software/guix/manual/en/html_node/Channels.html
+
+[debian/guix-package]: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=850644
+[fanquake/guix-docker]: https://github.com/fanquake/core-review/tree/master/guix
diff --git a/contrib/guix/guix-build.sh b/contrib/guix/guix-build.sh
new file mode 100755
index 0000000000..f8ba8c7ed2
--- /dev/null
+++ b/contrib/guix/guix-build.sh
@@ -0,0 +1,39 @@
+#!/usr/bin/env bash
+export LC_ALL=C
+set -e -o pipefail
+
+# Determine the maximum number of jobs to run simultaneously (overridable by
+# environment)
+MAX_JOBS="${MAX_JOBS:-$(nproc)}"
+
+# Download the depends sources now as we won't have internet access in the build
+# container
+make -C "${PWD}/depends" -j"$MAX_JOBS" download ${V:+V=1} ${SOURCES_PATH:+SOURCES_PATH="$SOURCES_PATH"}
+
+# Determine the reference time used for determinism (overridable by environment)
+SOURCE_DATE_EPOCH="${SOURCE_DATE_EPOCH:-$(git log --format=%at -1)}"
+
+# Deterministically build Bitcoin Core for HOSTs (overriable by environment)
+for host in ${HOSTS=i686-linux-gnu x86_64-linux-gnu arm-linux-gnueabihf aarch64-linux-gnu riscv64-linux-gnu}; do
+
+    # Display proper warning when the user interrupts the build
+    trap 'echo "** INT received while building ${host}, you may want to clean up the relevant output and distsrc-* directories before rebuilding"' INT
+
+    # Run the build script 'contrib/guix/libexec/build.sh' in the build
+    # container specified by 'contrib/guix/manifest.scm'
+    # shellcheck disable=SC2086
+    guix environment --manifest="${PWD}/contrib/guix/manifest.scm" \
+                     --container \
+                     --pure \
+                     --no-cwd \
+                     --share="$PWD"=/bitcoin \
+                     ${SOURCES_PATH:+--share="$SOURCES_PATH"} \
+                     ${ADDITIONAL_GUIX_ENVIRONMENT_FLAGS} \
+                     -- env HOST="$host" \
+                            MAX_JOBS="$MAX_JOBS" \
+                            SOURCE_DATE_EPOCH="${SOURCE_DATE_EPOCH:?unable to determine value}" \
+                            ${V:+V=1} \
+                            ${SOURCES_PATH:+SOURCES_PATH="$SOURCES_PATH"} \
+                          bash -c "cd /bitcoin && bash contrib/guix/libexec/build.sh"
+
+done
diff --git a/contrib/guix/libexec/build.sh b/contrib/guix/libexec/build.sh
new file mode 100644
index 0000000000..56b972a5cb
--- /dev/null
+++ b/contrib/guix/libexec/build.sh
@@ -0,0 +1,206 @@
+#!/usr/bin/env bash
+export LC_ALL=C
+set -e -o pipefail
+
+# Check that environment variables assumed to be set by the environment are set
+echo "Building for platform triple ${HOST:?not set} with reference timestamp ${SOURCE_DATE_EPOCH:?not set}..."
+echo "At most ${MAX_JOBS:?not set} jobs will run at once..."
+
+#####################
+# Environment Setup #
+#####################
+
+# The depends folder also serves as a base-prefix for depends packages for
+# $HOSTs after successfully building.
+BASEPREFIX="${PWD}/depends"
+
+# Setup an output directory for our build
+OUTDIR="${OUTDIR:-${PWD}/output}"
+[ -e "$OUTDIR" ] || mkdir -p "$OUTDIR"
+
+# Setup the directory where our Bitcoin Core build for HOST will occur
+DISTSRC="${DISTSRC:-${PWD}/distsrc-${HOST}}"
+if [ -e "$DISTSRC" ]; then
+    echo "DISTSRC directory '${DISTSRC}' exists, probably because of previous builds... Aborting..."
+    exit 1
+else
+    mkdir -p "$DISTSRC"
+fi
+
+# Given a package name and an output name, return the path of that output in our
+# current guix environment
+store_path() {
+    grep --extended-regexp "/[^-]{32}-${1}-cross-${HOST}-[^-]+${2:+-${2}}" "${GUIX_ENVIRONMENT}/manifest" \
+        | head --lines=1 \
+        | sed --expression='s|^[[:space:]]*"||' \
+              --expression='s|"[[:space:]]*$||'
+}
+
+# Determine output paths to use in CROSS_* environment variables
+CROSS_GLIBC="$(store_path glibc)"
+CROSS_GLIBC_STATIC="$(store_path glibc static)"
+CROSS_KERNEL="$(store_path linux-libre-headers)"
+CROSS_GCC="$(store_path gcc)"
+
+# Set environment variables to point Guix's cross-toolchain to the right
+# includes/libs for $HOST
+export CROSS_C_INCLUDE_PATH="${CROSS_GCC}/include:${CROSS_GLIBC}/include:${CROSS_KERNEL}/include"
+export CROSS_CPLUS_INCLUDE_PATH="${CROSS_GCC}/include/c++:${CROSS_GLIBC}/include:${CROSS_KERNEL}/include"
+export CROSS_LIBRARY_PATH="${CROSS_GLIBC}/lib:${CROSS_GLIBC_STATIC}/lib:${CROSS_GCC}/lib:${CROSS_GCC}/${HOST}/lib:${CROSS_KERNEL}/lib"
+
+# Disable Guix ld auto-rpath behavior
+export GUIX_LD_WRAPPER_DISABLE_RPATH=yes
+
+# Make /usr/bin if it doesn't exist
+[ -e /usr/bin ] || mkdir -p /usr/bin
+
+# Symlink file and env to a conventional path
+[ -e /usr/bin/file ] || ln -s --no-dereference "$(command -v file)" /usr/bin/file
+[ -e /usr/bin/env ]  || ln -s --no-dereference "$(command -v env)"  /usr/bin/env
+
+# Determine the correct value for -Wl,--dynamic-linker for the current $HOST
+glibc_dynamic_linker=$(
+    case "$HOST" in
+        i686-linux-gnu)      echo /lib/ld-linux.so.2 ;;
+        x86_64-linux-gnu)    echo /lib64/ld-linux-x86-64.so.2 ;;
+        arm-linux-gnueabihf) echo /lib/ld-linux-armhf.so.3 ;;
+        aarch64-linux-gnu)   echo /lib/ld-linux-aarch64.so.1 ;;
+        riscv64-linux-gnu)   echo /lib/ld-linux-riscv64-lp64d.so.1 ;;
+        *)                   exit 1 ;;
+    esac
+)
+
+# Environment variables for determinism
+export QT_RCC_TEST=1
+export QT_RCC_SOURCE_DATE_OVERRIDE=1
+export TAR_OPTIONS="--owner=0 --group=0 --numeric-owner --mtime='@${SOURCE_DATE_EPOCH}' --sort=name"
+export TZ="UTC"
+
+####################
+# Depends Building #
+####################
+
+# Build the depends tree, overriding variables that assume multilib gcc
+make -C depends --jobs="$MAX_JOBS" HOST="$HOST" \
+                                   ${V:+V=1} \
+                                   ${SOURCES_PATH+SOURCES_PATH="$SOURCES_PATH"} \
+                                   i686_linux_CC=i686-linux-gnu-gcc \
+                                   i686_linux_CXX=i686-linux-gnu-g++ \
+                                   i686_linux_AR=i686-linux-gnu-ar \
+                                   i686_linux_RANLIB=i686-linux-gnu-ranlib \
+                                   i686_linux_NM=i686-linux-gnu-nm \
+                                   i686_linux_STRIP=i686-linux-gnu-strip \
+                                   x86_64_linux_CC=x86_64-linux-gnu-gcc \
+                                   x86_64_linux_CXX=x86_64-linux-gnu-g++ \
+                                   x86_64_linux_AR=x86_64-linux-gnu-ar \
+                                   x86_64_linux_RANLIB=x86_64-linux-gnu-ranlib \
+                                   x86_64_linux_NM=x86_64-linux-gnu-nm \
+                                   x86_64_linux_STRIP=x86_64-linux-gnu-strip \
+                                   qt_config_opts_i686_linux='-platform linux-g++ -xplatform bitcoin-linux-g++'
+
+
+###########################
+# Source Tarball Building #
+###########################
+
+# Create the source tarball and move it to "${OUTDIR}/src" if not already there
+if [ -z "$(find "${OUTDIR}/src" -name 'bitcoin-*.tar.gz')" ]; then
+    ./autogen.sh
+    env CONFIG_SITE="${BASEPREFIX}/${HOST}/share/config.site" ./configure --prefix=/
+    make dist GZIP_ENV='-9n' ${V:+V=1}
+    mkdir -p "${OUTDIR}/src"
+    mv "$(find "${PWD}" -name 'bitcoin-*.tar.gz')" "${OUTDIR}/src/"
+fi
+
+# Determine the full path to our source tarball
+SOURCEDIST="$(find "${OUTDIR}/src" -name 'bitcoin-*.tar.gz')"
+# Determine our distribution name (e.g. bitcoin-0.18.0)
+DISTNAME="$(basename "$SOURCEDIST" '.tar.gz')"
+
+###########################
+# Binary Tarball Building #
+###########################
+
+# Create a spec file to normalize ssp linking behaviour
+spec_file="$(mktemp)"
+cat << EOF > "$spec_file"
+*link_ssp:
+%{fstack-protector|fstack-protector-all|fstack-protector-strong|fstack-protector-explicit:}
+EOF
+
+# Similar flags to Gitian
+CONFIGFLAGS="--enable-glibc-back-compat --enable-reduce-exports --disable-bench --disable-gui-tests"
+HOST_CFLAGS="-O2 -g -specs=${spec_file} -ffile-prefix-map=${PWD}=."
+HOST_CXXFLAGS="-O2 -g -specs=${spec_file} -ffile-prefix-map=${PWD}=."
+HOST_LDFLAGS="-Wl,--as-needed -Wl,--dynamic-linker=$glibc_dynamic_linker -static-libstdc++"
+
+# Make $HOST-specific native binaries from depends available in $PATH
+export PATH="${BASEPREFIX}/${HOST}/native/bin:${PATH}"
+(
+    cd "$DISTSRC"
+
+    # Extract the source tarball
+    tar --strip-components=1 -xf "${SOURCEDIST}"
+
+    # Configure this DISTSRC for $HOST
+    # shellcheck disable=SC2086
+    env CONFIG_SITE="${BASEPREFIX}/${HOST}/share/config.site" \
+        ./configure --prefix=/ \
+                    --disable-ccache \
+                    --disable-maintainer-mode \
+                    --disable-dependency-tracking \
+                    ${CONFIGFLAGS} \
+                    CFLAGS="${HOST_CFLAGS}" \
+                    CXXFLAGS="${HOST_CXXFLAGS}" \
+                    LDFLAGS="${HOST_LDFLAGS}"
+
+    sed -i.old 's/-lstdc++ //g' config.status libtool src/univalue/config.status src/univalue/libtool
+
+    # Build Bitcoin Core
+    make --jobs="$MAX_JOBS" ${V:+V=1}
+
+    # Perform basic ELF security checks on a series of executables.
+    make -C src --jobs=1 check-security ${V:+V=1}
+    # Check that executables only contain allowed gcc, glibc and libstdc++
+    # version symbols for Linux distro back-compatibility.
+    make -C src --jobs=1 check-symbols  ${V:+V=1}
+
+    # Setup the directory where our Bitcoin Core build for HOST will be
+    # installed. This directory will also later serve as the input for our
+    # binary tarballs.
+    INSTALLPATH="${PWD}/installed/${DISTNAME}"
+    mkdir -p "${INSTALLPATH}"
+    # Install built Bitcoin Core to $INSTALLPATH
+    make install DESTDIR="${INSTALLPATH}" ${V:+V=1}
+    (
+        cd installed
+
+        # Prune libtool and object archives
+        find . -name "lib*.la" -delete
+        find . -name "lib*.a" -delete
+
+        # Prune pkg-config files
+        rm -r "${DISTNAME}/lib/pkgconfig"
+
+        # Split binaries and libraries from their debug symbols
+        {
+            find "${DISTNAME}/bin" -type f -executable -print0
+            find "${DISTNAME}/lib" -type f -print0
+        } | xargs -0 -n1 -P"$MAX_JOBS" -I{} "${DISTSRC}/contrib/devtools/split-debug.sh" {} {} {}.dbg
+
+        cp "${DISTSRC}/doc/README.md" "${DISTNAME}/"
+
+        # Finally, deterministically produce {non-,}debug binary tarballs ready
+        # for release
+        find "${DISTNAME}" -not -name "*.dbg" -print0 \
+            | sort --zero-terminated \
+            | tar --create --no-recursion --mode='u+rw,go+r-w,a+X' --null --files-from=- \
+            | gzip -9n > "${OUTDIR}/${DISTNAME}-${HOST}.tar.gz" \
+            || ( rm -f "${OUTDIR}/${DISTNAME}-${HOST}.tar.gz" && exit 1 )
+        find "${DISTNAME}" -name "*.dbg" -print0 \
+            | sort --zero-terminated \
+            | tar --create --no-recursion --mode='u+rw,go+r-w,a+X' --null --files-from=- \
+            | gzip -9n > "${OUTDIR}/${DISTNAME}-${HOST}-debug.tar.gz" \
+            || ( rm -f "${OUTDIR}/${DISTNAME}-${HOST}-debug.tar.gz" && exit 1 )
+    )
+)
diff --git a/contrib/guix/manifest.scm b/contrib/guix/manifest.scm
new file mode 100644
index 0000000000..ca11d7a0f0
--- /dev/null
+++ b/contrib/guix/manifest.scm
@@ -0,0 +1,158 @@
+(use-modules (gnu)
+             (gnu packages)
+             (gnu packages autotools)
+             (gnu packages base)
+             (gnu packages bash)
+             (gnu packages check)
+             (gnu packages commencement)
+             (gnu packages compression)
+             (gnu packages cross-base)
+             (gnu packages file)
+             (gnu packages gawk)
+             (gnu packages gcc)
+             (gnu packages linux)
+             (gnu packages perl)
+             (gnu packages pkg-config)
+             (gnu packages python)
+             (gnu packages shells)
+             (guix build-system trivial)
+             (guix gexp)
+             (guix packages)
+             (guix profiles)
+             (guix utils))
+
+(define (make-ssp-fixed-gcc xgcc)
+  "Given a XGCC package, return a modified package that uses the SSP function
+from glibc instead of from libssp.so. Taken from:
+http://www.linuxfromscratch.org/hlfs/view/development/chapter05/gcc-pass1.html"
+  (package
+   (inherit xgcc)
+   (arguments
+    (substitute-keyword-arguments (package-arguments xgcc)
+      ((#:make-flags flags)
+       `(cons "gcc_cv_libc_provides_ssp=yes" ,flags))))))
+
+(define (make-gcc-rpath-link xgcc)
+  "Given a XGCC package, return a modified package that replace each instance of
+-rpath in the default system spec that's inserted by Guix with -rpath-link"
+  (package
+   (inherit xgcc)
+   (arguments
+    (substitute-keyword-arguments (package-arguments xgcc)
+      ((#:phases phases)
+       `(modify-phases ,phases
+          (add-after 'pre-configure 'replace-rpath-with-rpath-link
+            (lambda _
+              (substitute* (cons "gcc/config/rs6000/sysv4.h"
+                                 (find-files "gcc/config"
+                                             "^gnu-user.*\\.h$"))
+                (("-rpath=") "-rpath-link="))
+              #t))))))))
+
+(define (make-cross-toolchain target
+                              base-gcc-for-libc
+                              base-kernel-headers
+                              base-libc
+                              base-gcc)
+  "Create a cross-compilation toolchain package for TARGET"
+  (let* ((xbinutils (cross-binutils target))
+         ;; 1. Build a cross-compiling gcc without targeting any libc, derived
+         ;; from BASE-GCC-FOR-LIBC
+         (xgcc-sans-libc (cross-gcc target
+                                    #:xgcc base-gcc-for-libc
+                                    #:xbinutils xbinutils))
+         ;; 2. Build cross-compiled kernel headers with XGCC-SANS-LIBC, derived
+         ;; from BASE-KERNEL-HEADERS
+         (xkernel (cross-kernel-headers target
+                                        base-kernel-headers
+                                        xgcc-sans-libc
+                                        xbinutils))
+         ;; 3. Build a cross-compiled libc with XGCC-SANS-LIBC and XKERNEL,
+         ;; derived from BASE-LIBC
+         (xlibc (cross-libc target
+                            base-libc
+                            xgcc-sans-libc
+                            xbinutils
+                            xkernel))
+         ;; 4. Build a cross-compiling gcc targeting XLIBC, derived from
+         ;; BASE-GCC
+         (xgcc (cross-gcc target
+                          #:xgcc base-gcc
+                          #:xbinutils xbinutils
+                          #:libc xlibc)))
+    ;; Define a meta-package that propagates the resulting XBINUTILS, XLIBC, and
+    ;; XGCC
+    (package
+      (name (string-append target "-toolchain"))
+      (version (package-version xgcc))
+      (source #f)
+      (build-system trivial-build-system)
+      (arguments '(#:builder (begin (mkdir %output) #t)))
+      (propagated-inputs
+       `(("binutils" ,xbinutils)
+         ("libc" ,xlibc)
+         ("libc:static" ,xlibc "static")
+         ("gcc" ,xgcc)))
+      (synopsis (string-append "Complete GCC tool chain for " target))
+      (description (string-append "This package provides a complete GCC tool
+chain for " target " development."))
+      (home-page (package-home-page xgcc))
+      (license (package-license xgcc)))))
+
+(define* (make-bitcoin-cross-toolchain target
+                                  #:key
+                                  (base-gcc-for-libc gcc-5)
+                                  (base-kernel-headers linux-libre-headers-4.19)
+                                  (base-libc glibc-2.27)
+                                  (base-gcc (make-gcc-rpath-link
+                                             (make-ssp-fixed-gcc gcc-9))))
+  "Convienience wrapper around MAKE-CROSS-TOOLCHAIN with default values
+desirable for building Bitcoin Core release binaries."
+  (make-cross-toolchain target
+                   base-gcc-for-libc
+                   base-kernel-headers
+                   base-libc
+                   base-gcc))
+
+(packages->manifest
+ (list ;; The Basics
+       bash-minimal
+       which
+       coreutils
+       util-linux
+       ;; File(system) inspection
+       file
+       grep
+       diffutils
+       findutils
+       ;; File transformation
+       patch
+       gawk
+       sed
+       ;; Compression and archiving
+       tar
+       bzip2
+       gzip
+       xz
+       zlib
+       ;; Build tools
+       gnu-make
+       libtool
+       autoconf
+       automake
+       pkg-config
+       ;; Scripting
+       perl
+       python-3.7
+       ;; Native gcc 9 toolchain targeting glibc 2.27
+       (make-gcc-toolchain gcc-9 glibc-2.27)
+       ;; Cross gcc 9 toolchains targeting glibc 2.27
+       (make-bitcoin-cross-toolchain "i686-linux-gnu")
+       (make-bitcoin-cross-toolchain "x86_64-linux-gnu")
+       (make-bitcoin-cross-toolchain "aarch64-linux-gnu")
+       (make-bitcoin-cross-toolchain "arm-linux-gnueabihf")
+       ;; The glibc 2.27 for riscv64 needs gcc 7 to successfully build (see:
+       ;; https://www.gnu.org/software/gcc/gcc-7/changes.html#riscv). The final
+       ;; toolchain is still a gcc 9 toolchain targeting glibc 2.27.
+       (make-bitcoin-cross-toolchain "riscv64-linux-gnu"
+                                     #:base-gcc-for-libc gcc-7)))
diff --git a/depends/packages/qt.mk b/depends/packages/qt.mk
index 23cde9ee6d..7c7081eaba 100644
--- a/depends/packages/qt.mk
+++ b/depends/packages/qt.mk
@@ -160,7 +160,8 @@ define $(package)_preprocess_cmds
   echo "QMAKE_LINK_OBJECT_SCRIPT = object_script" >> qtbase/mkspecs/win32-g++/qmake.conf &&\
   sed -i.old "s|QMAKE_CFLAGS            = |!host_build: QMAKE_CFLAGS            = $($(package)_cflags) $($(package)_cppflags) |" qtbase/mkspecs/win32-g++/qmake.conf && \
   sed -i.old "s|QMAKE_LFLAGS            = |!host_build: QMAKE_LFLAGS            = $($(package)_ldflags) |" qtbase/mkspecs/win32-g++/qmake.conf && \
-  sed -i.old "s|QMAKE_CXXFLAGS          = |!host_build: QMAKE_CXXFLAGS            = $($(package)_cxxflags) $($(package)_cppflags) |" qtbase/mkspecs/win32-g++/qmake.conf
+  sed -i.old "s|QMAKE_CXXFLAGS          = |!host_build: QMAKE_CXXFLAGS            = $($(package)_cxxflags) $($(package)_cppflags) |" qtbase/mkspecs/win32-g++/qmake.conf && \
+  sed -i.old "s/LIBRARY_PATH/(CROSS_)?\0/g" qtbase/mkspecs/features/toolchain.prf
 endef
 
 define $(package)_config_cmds