I used fpcupdeluxe to download FPC trunk rather than via a version control system, as I haven't used one before. I have only ever used the command line version of Git that is part of MSYS2 and even then I did not make any changes to the downloaded code before compiling.
The command line version of Git is what I use as well though without MSYS2, but Git for Windosw directly. But you can see what I meant also in the web interface which is why I gave you that link.
Then you might have to wait a long time, because it's a very low priority task on my very long ToDo list.
It isn't that high a priority for me either, as so few Z80 machines even had more than 64Kb of memory.
I would also have a lot to learn before I could add support for another machine to the same level as you have already done for MSX-DOS.
Adding a new target is a rather nice beginner task, in fact that was what I had started with as well around 10 years ago. In addition to my adding of MSX-DOS you can also take a look
here. The guide
might be a bit old, but in general it should still work.