Merge #20601: doc: Update for FreeBSD 12.2, add GUI Build Instructions

c17569056105d221053a839d5430df5b3e94f746 doc: Update for FreeBSD 12.2, add GUI Build Instructions (Jarol Rodriguez)

Pull request description:

  The current FreeBSD Build documentation is a little outdated and underwhelming. This PR intends to keep the build-freebsd.md doc up to date. Here are the main improvements:
  - Introduce dependency information
  - New instructions for building the GUI
  - Instructions for supporting descriptor wallets
  - Various notes on the build and compile process

  **Before/Master:** [render](https://github.com/bitcoin/bitcoin/blob/master/doc/build-freebsd.md)

  **After/PR:** [render](https://github.com/bitcoin/bitcoin/blob/2e8b9a5aac2a2c8926216a971c87ea8f8c00cb1b/doc/build-freebsd.md)

ACKs for top commit:
  laanwj:
    utACK c17569056105d221053a839d5430df5b3e94f746

Tree-SHA512: 64aeb743c7f4ed167451454564b53d13c5c30d82bd2423799655c7b5b465a75733072fb0c574927c2588a46e89a68c6c57b008220acfd25336d445c9dc309f3b

1 files changed, 90 insertions, 22 deletions

diff --git a/doc/build-freebsd.md b/doc/build-freebsd.md
index f48855a344..18ea84c579 100644
--- a/doc/build-freebsd.md
+++ b/doc/build-freebsd.md
@@ -1,59 +1,127 @@
-FreeBSD build guide
-======================
-(updated for FreeBSD 12.0)
+# FreeBSD Build Guide
 
-This guide describes how to build bitcoind and command-line utilities on FreeBSD.
+**Updated for FreeBSD [12.2](https://www.freebsd.org/releases/12.2R/announce.html)**
 
-This guide does not contain instructions for building the GUI.
+This guide describes how to build bitcoind, command-line utilities, and GUI on FreeBSD.
+
+## Dependencies
+
+The following dependencies are **required**:
+
+ Library                                                               | Purpose    | Description
+ ----------------------------------------------------------------------|------------|----------------------
+ [autoconf](https://svnweb.freebsd.org/ports/head/devel/autoconf/)     | Build      | Automatically configure software source code
+ [automake](https://svnweb.freebsd.org/ports/head/devel/automake/)     | Build      | Generate makefile (requires autoconf)
+ [libtool](https://svnweb.freebsd.org/ports/head/devel/libtool/)       | Build      | Shared library support
+ [pkgconf](https://svnweb.freebsd.org/ports/head/devel/pkgconf/)       | Build      | Configure compiler and linker flags
+ [git](https://svnweb.freebsd.org/ports/head/devel/git/)               | Clone      | Version control system
+ [gmake](https://svnweb.freebsd.org/ports/head/devel/gmake/)           | Compile    | Generate executables
+ [boost-libs](https://svnweb.freebsd.org/ports/head/devel/boost-libs/) | Utility    | Library for threading, data structures, etc
+ [libevent](https://svnweb.freebsd.org/ports/head/devel/libevent/)     | Networking | OS independent asynchronous networking
+
+
+The following dependencies are **optional**:
+
+  Library                                                                    | Purpose          | Description
+  ---------------------------------------------------------------------------|------------------|----------------------
+  [db5](https://svnweb.freebsd.org/ports/head/databases/db5/)                | Berkeley DB      | Wallet storage (only needed when wallet enabled)
+  [qt5](https://svnweb.freebsd.org/ports/head/devel/qt5/)                    | GUI              | GUI toolkit (only needed when GUI enabled)
+  [libqrencode](https://svnweb.freebsd.org/ports/head/graphics/libqrencode/) | QR codes in GUI  | Generating QR codes (only needed when GUI enabled)
+  [libzmq4](https://svnweb.freebsd.org/ports/head/net/libzmq4/)              | ZMQ notification | Allows generating ZMQ notifications (requires ZMQ version >= 4.0.0)
+  [sqlite3](https://svnweb.freebsd.org/ports/head/databases/sqlite3/)        | SQLite DB        | Wallet storage (only needed when wallet enabled)
+  [python3](https://svnweb.freebsd.org/ports/head/lang/python3/)             | Testing          | Python Interpreter (only needed when running the test suite)
+
+  See [dependencies.md](dependencies.md) for a complete overview.
 
 ## Preparation
 
-You will need the following dependencies, which can be installed as root via pkg:
+### 1. Install Required Dependencies
+Install the required dependencies the usual way you [install software on FreeBSD](https://www.freebsd.org/doc/en/books/handbook/ports.html) - either with `pkg` or via the Ports collection. The example commands below use `pkg` which is usually run as `root` or via `sudo`. If you want to use `sudo`, and you haven't set it up: [use this guide](http://www.freebsdwiki.net/index.php/Sudo%2C_configuring) to setup `sudo` access on FreeBSD.
 
 ```bash
 pkg install autoconf automake boost-libs git gmake libevent libtool pkgconf
 
+```
+
+### 2. Clone Bitcoin Repo
+Now that `git` and all the required dependencies are installed, let's clone the Bitcoin Core repository to a directory. All build scripts and commands will run from this directory.
+``` bash
 git clone https://github.com/bitcoin/bitcoin.git
 ```
 
-In order to run the test suite (recommended), you will need to have Python 3 installed:
+### 3. Install Optional Dependencies
+
+#### Wallet Dependencies
+It is not necessary to build wallet functionality to run bitcoind or the GUI. To enable legacy wallets, you must install `db5`. To enable [descriptor wallets](https://github.com/bitcoin/bitcoin/blob/master/doc/descriptors.md), `sqlite3` is required. Skip `db5` if you intend to *exclusively* use descriptor wallets
+
+###### Legacy Wallet Support
+`db5` is required to enable support for legacy wallets. Skip if you don't intend to use legacy wallets
 
 ```bash
-pkg install python3
+pkg install db5
 ```
 
-See [dependencies.md](dependencies.md) for a complete overview.
+###### Descriptor Wallet Support
 
-### Building BerkeleyDB
+`sqlite3` is required to enable support for descriptor wallets. Skip if you don't intend to use descriptor wallets.
+``` bash
+pkg install sqlite3
+```
+---
 
-BerkeleyDB is only necessary for the wallet functionality. To skip this, pass
-`--disable-wallet` to `./configure` and skip to the next section.
+#### GUI Dependencies
+###### Qt5
 
+Bitcoin Core includes a GUI built with the cross-platform Qt Framework. To compile the GUI, we need to install `qt5`. Skip if you don't intend to use the GUI.
 ```bash
-./contrib/install_db4.sh `pwd`
-export BDB_PREFIX="$PWD/db4"
+pkg install qt5
 ```
+###### libqrencode
+
+The GUI can encode addresses in a QR Code. To build in QR support for the GUI, install `libqrencode`. Skip if not using the GUI or don't want QR code functionality.
+```bash
+pkg install libqrencode
+```
+---
+
+#### Test Suite Dependencies
+There is an included test suite that is useful for testing code changes when developing.
+To run the test suite (recommended), you will need to have Python 3 installed:
+
+```bash
+pkg install python3
+```
+---
 
 ## Building Bitcoin Core
 
-**Important**: Use `gmake` (the non-GNU `make` will exit with an error).
+### 1. Configuration
 
-With wallet:
+There are many ways to configure Bitcoin Core, here are a few common examples:
+##### Wallet (BDB + SQlite) Support, No GUI:
+This explicitly enables legacy wallet support and disables the GUI. If `sqlite3` is installed, then descriptor wallet support will be built.
 ```bash
 ./autogen.sh
-./configure --with-gui=no \
-    BDB_LIBS="-L${BDB_PREFIX}/lib -ldb_cxx-4.8" \
-    BDB_CFLAGS="-I${BDB_PREFIX}/include" \
+./configure --with-gui=no --with-incompatible-bdb \
+    BDB_LIBS="-ldb_cxx-5" \
+    BDB_CFLAGS="-I/usr/local/include/db5" \
     MAKE=gmake
 ```
 
-Without wallet:
+##### Wallet (only SQlite) and GUI Support:
+This explicitly enables the GUI and disables legacy wallet support. If `qt5` is not installed, this will throw an error. If `sqlite3` is installed then descriptor wallet functionality will be built. If `sqlite3` is not installed, then wallet functionality will be disabled.
 ```bash
 ./autogen.sh
-./configure --with-gui=no --disable-wallet MAKE=gmake
+./configure --without-bdb --with-gui=yes MAKE=gmake
+```
+##### No Wallet or GUI
+``` bash
+./autogen.sh
+./configure --without-wallet --with-gui=no MAKE=gmake
 ```
 
-followed by:
+### 2. Compile
+**Important**: Use `gmake` (the non-GNU `make` will exit with an error).
 
 ```bash
 gmake # use -jX here for parallelism