contrib: mingw64: update d3d12

Qt 6.7 requires[1] __ID3D12Device2_INTERFACE_DEFINED__
for d3d12 abstraction which comes with MinGW64 v12.

[1] qrhid3d12_p.h @ L32:
// ID3D12Device2 and ID3D12GraphicsCommandList1 and types and enums introduced
// with those are hard requirements now. These should be declared in any
// moderately recent d3d12.h, but if it is an SDK from before Windows 10
// version 1703 then these types could be missing. In the absence of other
// options, handle this by skipping all the code and making QRhi::create() fail
// in such builds.

contrib/src/mingw64/rules.mak

@@ -16,12 +16,9 @@ PKGS += dcomp
 endif # !HAVE_WINSTORE
 PKGS += dxva dxvahd mingw11-fixes mft10 d3d12
 
-ifeq ($(call mingw_at_least, 9), true)
-PKGS_FOUND += d3d12
 ifdef HAVE_WINSTORE
 PKGS_FOUND += winrt_headers
 endif # HAVE_WINSTORE
-endif # MINGW 9
 ifeq ($(call mingw_at_least, 10), true)
 PKGS_FOUND += dxva mft10
 endif # MINGW 10
@@ -32,7 +29,7 @@ ifeq ($(call mingw_at_least, 11), true)
 PKGS_FOUND += dxvahd
 endif # MINGW 11
 ifeq ($(call mingw_at_least, 12), true)
-PKGS_FOUND += mingw11-fixes
+PKGS_FOUND += mingw11-fixes d3d12
 endif # MINGW 12
 endif # !HAVE_VISUALSTUDIO