contrib: don't depend on headers available in mingw-w64

(cherry picked from commit bdb36c1b)
Signed-off-by: Rafaël Carré <funman@videolan.org>

contrib/src/directx/rules.mak

@@ -4,8 +4,10 @@ DX_HEADERS_URL := $(CONTRIB_VIDEOLAN)/directx-oss.tar.bz2
 DXVA2_URL := $(CONTRIB_VIDEOLAN)/dxva2api.h
 
 ifdef HAVE_WIN32
+ifndef HAVE_MINGW_W64
 PKGS += directx
 endif
+endif
 
 $(TARBALLS)/directx-oss.tar.bz2:
 	$(call download,$(DX_HEADERS_URL))

contrib/src/dshow/rules.mak

@@ -6,8 +6,10 @@ D2D_URL := http://nodeload.github.com/2of1/d2d1headers/tarball/master
 # FIXME: ^ D2D not working
 
 ifdef HAVE_WIN32
+ifndef HAVE_MINGW_W64
 PKGS += dshow
 endif
+endif
 
 $(TARBALLS)/dshow-headers-oss.tar.bz2:
 	$(call download,$(DSHOW_HEADERS_URL))

contrib/src/ffmpeg/rules.mak

@@ -77,7 +77,9 @@ endif
 
 # Windows
 ifdef HAVE_WIN32
+ifndef HAVE_MINGW_W64
 DEPS_ffmpeg += directx
+endif
 FFMPEGCONF += --target-os=mingw32 --enable-memalign-hack
 FFMPEGCONF += --enable-w32threads \
 	--disable-bzlib --disable-bsfs \