Meson build system for distros

[mia-0]

I got sidetracked and packaged gitstatus while setting up p10k because, to put it mildly, I really don’t like it when something downloads and runs random untrusted executables behind my back.

Anyway, this makes building gitstatusd in a way that works for e.g. Linux distributions very easy. Usually, the following is sufficient:

meson setup builddir
meson compile -C builddir
meson install -C builddir --skip-subprojects

Meson will automatically fetch the libgit2 fork (see subprojects/libgit2.wrap) and build it as internal dependency. It will try to use system libraries for the few dependencies that cannot be disabled.

Version info is read from build.info, but the Wrap file duplicates the Git ref for libgit2.

I did not attempt to replace the existing build scripts, but that should be trivial if desired.