Merge #17595: guix: Enable building for `x86_64-w64-mingw32` target

a35e3235891d35daa167116cc70340140e883f06 guix: Appease travis. (Carl Dong)
0b66d22da5f53640e22f05adf880782c613e6d0f guix: Use gcc-9 for mingw-w64 instead of 8 (Carl Dong)
ba0b99bdd613ba7f17c6247ece3001e1b44759a3 guix: Don't set MINGW_HAS_SECURE_API CFLAG in depends (Carl Dong)
93439a71eda49fb69f1e82966a23a946733aa6fa guix: Bump to upstream commit with mingw-w64 changes (Carl Dong)
35a96792dda9e78165b1598aeac7b2ab759e7be5 guix: Check mingw symbols, improve SSP fix docs (Carl Dong)
449d8fe25bbe25daacfc67aa89ca32b0a3254c5a guix: Expand on INT trap message (Carl Dong)
3f1f03c67a8e9edf487f08d272adb18b0a3942c8 guix: Spelling fixes (Carl Dong)
ff821dd2a1c600488d11e7d9a20e9179ecc9144b guix: Reinstate make-ssp-fixed-gcc (Carl Dong)
360a9e0ad50a36ec79a1a160dbed3966689fd41c guix: Bump time-machine for mingw-w64 patches (Carl Dong)
93e41b7e3b54c17fd1b4c61ee95fc0dc2827e954 guix: Use gcc-8 for mingw-w64 instead of 7 (Carl Dong)
ef4f7e4c45c60a69406134122f091c77c6ef740f guix: Set the well-known timezone env var (Carl Dong)
acf4b3b3b5accf60a19441a0298ef27001b78e72 guix: Make x86_64-w64-mingw32 builds reproducible (Carl Dong)
c4cce00eac691625b78b92f7dba0b7f57def19e5 guix: Remove dead links from README. (Carl Dong)
df953a4c9a6143f45864757b706c88b6fa70545a guix: Appease shellcheck. (Carl Dong)
91897c95e191d293eb27d8af15cbeafc5b8f3895 guix: Improve guix-build.sh documentation (Carl Dong)
570d769c6c59b9f6d1a2b95b2ed60432cb33b3ba guix: Build support for Windows (Carl Dong)

Pull request description:

  ~~Based on: https://github.com/bitcoin/bitcoin/pull/16519~~
  Based on: #17933 (Time Machines are... shall we say... superior :grin:)

  This PR allows us to perform Guix builds for the `x86_64-w64-mingw32` target. We do this _without_ splitting up the build script like we do in Gitian by using this newfangled alien technology called `case` statements. (This is WIP and might be changed to `if` statements soon)

ACKs for top commit:
  fanquake:
    ACK a35e3235891d35daa167116cc70340140e883f06 2/3

Tree-SHA512: c471951c23eb2cda919a71285d8b8f2580cb20f09d5db17b53e13dbd8813e01b3e7a83ea848e4913fd0f2bc12c6c133c5f76b54e65c0d89fed4dfd2e0be19875

1 files changed, 94 insertions, 21 deletions

diff --git a/contrib/guix/guix-build.sh b/contrib/guix/guix-build.sh
index 2daa8aba5e..e20b2a048d 100755
--- a/contrib/guix/guix-build.sh
+++ b/contrib/guix/guix-build.sh
@@ -13,33 +13,106 @@ make -C "${PWD}/depends" -j"$MAX_JOBS" download ${V:+V=1} ${SOURCES_PATH:+SOURCE
 # Determine the reference time used for determinism (overridable by environment)
 SOURCE_DATE_EPOCH="${SOURCE_DATE_EPOCH:-$(git log --format=%at -1)}"
 
+# Execute "$@" in a pinned, possibly older version of Guix, for reproducibility
+# across time.
 time-machine() {
     guix time-machine --url=https://github.com/dongcarl/guix.git \
-                      --commit=b3a7c72c8b2425f8ddb0fc6e3b1caeed40f86dee \
+                      --commit=b066c25026f21fb57677aa34692a5034338e7ee3 \
                       -- "$@"
 }
 
-# Deterministically build Bitcoin Core for HOSTs (overriable by environment)
-for host in ${HOSTS=x86_64-linux-gnu arm-linux-gnueabihf aarch64-linux-gnu riscv64-linux-gnu}; do
+# Function to be called when building for host ${1} and the user interrupts the
+# build
+int_trap() {
+cat << EOF
+** INT received while building ${1}, you may want to clean up the relevant
+   output, deploy, and distsrc-* directories before rebuilding
+
+Hint: To blow everything away, you may want to use:
+
+  $ git clean -xdff --exclude='/depends/SDKs/*'
+
+Specifically, this will remove all files without an entry in the index,
+excluding the SDK directory. Practically speaking, this means that all ignored
+and untracked files and directories will be wiped, allowing you to start anew.
+EOF
+}
+
+# Deterministically build Bitcoin Core for HOSTs (overridable by environment)
+# shellcheck disable=SC2153
+for host in ${HOSTS=x86_64-linux-gnu arm-linux-gnueabihf aarch64-linux-gnu riscv64-linux-gnu x86_64-w64-mingw32}; do
 
     # Display proper warning when the user interrupts the build
-    trap 'echo "** INT received while building ${host}, you may want to clean up the relevant output and distsrc-* directories before rebuilding"' INT
-
-    # Run the build script 'contrib/guix/libexec/build.sh' in the build
-    # container specified by 'contrib/guix/manifest.scm'
-    # shellcheck disable=SC2086
-    time-machine environment --manifest="${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"
+    trap 'int_trap ${host}' INT
+
+    (
+        # Required for 'contrib/guix/manifest.scm' to output the right manifest
+        # for the particular $HOST we're building for
+        export HOST="$host"
+
+        # Run the build script 'contrib/guix/libexec/build.sh' in the build
+        # container specified by 'contrib/guix/manifest.scm'.
+        #
+        # Explanation of `guix environment` flags:
+        #
+        #   --container        run command within an isolated container
+        #
+        #     Running in an isolated container minimizes build-time differences
+        #     between machines and improves reproducibility
+        #
+        #   --pure             unset existing environment variables
+        #
+        #     Same rationale as --container
+        #
+        #   --no-cwd           do not share current working directory with an
+        #                      isolated container
+        #
+        #     When --container is specified, the default behavior is to share
+        #     the current working directory with the isolated container at the
+        #     same exact path (e.g. mapping '/home/satoshi/bitcoin/' to
+        #     '/home/satoshi/bitcoin/'). This means that the $PWD inside the
+        #     container becomes a source of irreproducibility. --no-cwd disables
+        #     this behaviour.
+        #
+        #   --share=SPEC       for containers, share writable host file system
+        #                      according to SPEC
+        #
+        #   --share="$PWD"=/bitcoin
+        #
+        #                     maps our current working directory to /bitcoin
+        #                     inside the isolated container, which we later cd
+        #                     into.
+        #
+        #     While we don't want to map our current working directory to the
+        #     same exact path (as this introduces irreproducibility), we do want
+        #     it to be at a _fixed_ path _somewhere_ inside the isolated
+        #     container so that we have something to build. '/bitcoin' was
+        #     chosen arbitrarily.
+        #
+        #   ${SOURCES_PATH:+--share="$SOURCES_PATH"}
+        #
+        #                     make the downloaded depends sources path available
+        #                     inside the isolated container
+        #
+        #     The isolated container has no network access as it's in a
+        #     different network namespace from the main machine, so we have to
+        #     make the downloaded depends sources available to it. The sources
+        #     should have been downloaded prior to this invocation.
+        #
+        # shellcheck disable=SC2086
+        time-machine 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