Makefile cleanup and simplify ARM stuff.
Makefile cleanup and simplify ARM stuff.

sergiobenrocha2/mgba,sergiobenrocha2/mgba,sergiobenrocha2/mgba,sergiobenrocha2/mgba,libretro/mgba,libretro/mgba,fr500/mgba,sergiobenrocha2/mgba,fr500/mgba,fr500/mgba,libretro/mgba,fr500/mgba,libretro/mgba,libretro/mgba