contrib: avoid Darwin patch on other systems

(cherry picked from commit 0e00a98a)

Conflicts:

	extras/contrib/src/Makefile

extras/contrib/src/Makefile

@@ -1027,11 +1027,13 @@ endif
 ifdef HAVE_BEOS
 	(cd $@; patch -p0 < ../Patches/ffmpeg-alignment.patch)
 endif
+ifdef HAVE_DARWIN_OS
 ifdef HAVE_DARWIN_OS_ON_INTEL
 	(cd $@; patch -p0 < ../Patches/ffmpeg-macosx-intel-mmx.patch)
 else
 	(cd $@; patch -p0 < ../Patches/ffmpeg-darwin-ppc-mdynamic.patch) 
 endif
+endif
 ifdef HAVE_UCLIBC
 	patch -p0 < Patches/ffmpeg-svn-uclibc.patch
 	patch -p0 < Patches/ffmpeg-svn-internal-define.patch