more windows confusions

[Phillip Lord]

I'm currently scripting the windows build and have hit a snag. My
dependency list has two packages for which there do not appear to be
source.

The two in question are these:

mingw-w64-gcc-libs
mingw-w64-libwinpthread-git

Both pretty generic and indirect dependencies of most of the Emacs
libraries dependencies. I'm trying to get the source from here.

https://github.com/Alexpux/MINGW-packages

I'm guessing this is because of some obscurity about the way packaging
works for MSYS2/MINGW. Any suggestions welcome.

Phil