path separator for mingw
path separator in glib2 depends on OS being windows "" or linux "/"
but there's a mixing OS "mingw" where you're on windows, but your paths are like linux.
win32unix out there to deal with this:
Is possible to detect this mixed OS system on meson and build glib2 on msys that way?
This is hitting gitg on windows (which is build on mingw) gitg#66 (moved)