cmake: look for png.h, not libpng.h

libpng ships png.h, so look for that instead of libpng.h

Change-Id: Ifdbe0fca9e5b93973653a94e6ab800f1bfad8ecf
Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
1 file changed