CMake: Clean up ref names in git branch string (fixes #2421)
CMake: Clean up ref names in git branch string (fixes #2421)

libretro/mgba,Iniquitatis/mgba,mgba-emu/mgba,mgba-emu/mgba,libretro/mgba,libretro/mgba,Iniquitatis/mgba,libretro/mgba,Iniquitatis/mgba,mgba-emu/mgba,mgba-emu/mgba,Iniquitatis/mgba,libretro/mgba