Tested on macOS 12.5:
brew install meson python3 py3cairo pygobject3 gtk+3
meson setup build
cd build
meson compile
meson test
meson install
After `meson install`, `diffuse` can be used to launch a
native Mac app that is installed into /Applications/Diffuse.app.
These steps could be put into a Homebrew formula, see
https://docs.brew.sh/Formula-Cookbook, as a way to
distribute Diffuse on macOS.
Here we strip away Linux-only stuff so devs
can create a local "Mac build".
There might be other Linux-only stuff that
are not needed on Mac still. Follow-ups are
welcome.