force WINAPI_FAMILY to WINAPI_FAMILY_DESKTOP_APP to be able to use dxva.h

The struct definitions in dxva.h, which are necessary in order to
actually use d3d11va, are hidden when WINAPI_FAMILY targets Windows Phone
or WindowsRT.

Building with WINAPI_FAMILY=WINAPI_FAMILY_DESKTOP_APP is disallowed
when targeting ARM. ("Compiling Desktop applications for the ARM
platform is not supported.") So we set _CRT_BUILD_DESKTOP_APP to 0
to tell the runtime not to detect some issues with this mismatching.

The same tweaks to detect if the API is available is done in dxva2_internal.h
when compiling each DXVA2/D3D11VA decoders.
Signed-off-by: Martin Storsjö <martin@martin.st>

configure

@@ -4270,7 +4270,7 @@ check_lib2 "windows.h psapi.h" GetProcessMemoryInfo -lpsapi
 
 check_struct "sys/time.h sys/resource.h" "struct rusage" ru_maxrss
 
-check_type "windows.h dxva.h" "DXVA_PicParams_HEVC"
+check_type "windows.h dxva.h" "DXVA_PicParams_HEVC" -DWINAPI_FAMILY=WINAPI_FAMILY_DESKTOP_APP -D_CRT_BUILD_DESKTOP_APP=0
 check_type "windows.h d3d11.h" "ID3D11VideoDecoder"
 check_type "d3d9.h dxva2api.h" DXVA2_ConfigPictureDecode -D_WIN32_WINNT=0x0600
 

libavcodec/dxva2_internal.h

@@ -27,6 +27,9 @@
 
 #include "config.h"
 
+/* define the proper COM entries before forcing desktop APIs */
+#include <objbase.h>
+
 #if CONFIG_DXVA2
 #include "dxva2.h"
 #endif
@@ -34,6 +37,12 @@
 #include "d3d11va.h"
 #endif
 #if HAVE_DXVA_H
+/* When targeting WINAPI_FAMILY_PHONE_APP or WINAPI_FAMILY_APP, dxva.h
+ * defines nothing. Force the struct definitions to be visible. */
+#undef WINAPI_FAMILY
+#define WINAPI_FAMILY WINAPI_FAMILY_DESKTOP_APP
+#undef _CRT_BUILD_DESKTOP_APP
+#define _CRT_BUILD_DESKTOP_APP 0
 #include <dxva.h>
 #endif