Make sure PNGCPP is actually used when USE_LIB_PNGCPP is set.
Make sure PNGCPP is actually used when USE_LIB_PNGCPP is set.

OpenRhythm/OpenRhythm,OpenRhythm/OpenRhythm,OpenRhythm/OpenRhythm,mdsitton/musicgame,mdsitton/musicgame