Simplest source build of v22.0

Since I was setting up an new Ubuntu 21.10 machine, I decided to do a quick bitcoin build and help anyone out who hasn't tried doing a build yet. Essentially you build the library dependencies, then you build bitcoin. Pretty simple but I did manage to get tripped up a bit. Here's the simplest path for those interested

sudo apt install -y build-essential libtool autotools-dev automake pkg-config bsdmainutils python3 tag="v22.0" srcdir="$HOME/src/bitcoin" deps="$srcdir/depends" conf="$deps/$MACHTYPE/share/config.site" libpath="$deps/$MACHTYPE/lib" mkdir -p "$srcdir" git clone -b $tag https://github.com/bitcoin/bitcoin.git $srcdir cd $deps make # -j N ## for multicore cd "$srcdir" ./autogen.sh CONFIG_SITE=$conf ./configure make # -j N ## for multicore LD_LIBRARY_PATH="$libpath:$LD_LIBRARY_PATH" $srcdir/src/qt/bitcoin-qt & 

And here's the breakdown.

1. Install the build utilities and compilers (sudo apt ...)
2. Set up some local variable names (tag, srcdir, deps, conf, libpath)
3. Make a local src directory to hold the build
4. Copy (clone) version 22.0 (tag) of the source down into our directory
5. Switch to the deps (depends) directory
6. Make the library dependencies
7. Switch to the main source directory
8. Run autogen
9. Tell configure that we built all the libraries and share it in CONFIG_SITE
10. Make the bitcoin binaries
11. Run bitcoin-qt making sure your freshly built libraries are in the path

Anyway, like I said, I got tripped up for some reason on CONFIG_SITE and LD_LIBRARY_PATH since I've been away from Linux for a while.

Next up is to try the Guix build. I just did a Nix build of the Trezor firmware and that wasn't to bad, so hopefully running Guix on Ubuntu won't be too bad either.