Bug 1536308 - Apply a local patch to MinGW to get the needed winrt stuff for ANGLE r=froydnj

We apply a local patch while we wait for upstream wine and mingw to review
the changes to widl that are necessary to generate the correct headers. Here we
just grab the generated headers and patch them into MinGW

We can revert this when MinGW updates, but for now we would like to unblock
the ANGLE update

Depends on D25294

Differential Revision: https://phabricator.services.mozilla.com/D25295

--HG--
extra : moz-landing-system : lando

taskcluster/scripts/misc/build-clang-trunk-mingw.sh

@@ -47,6 +47,7 @@ default_win32_winnt=0x601
 cd $HOME_DIR/src
 
 . taskcluster/scripts/misc/tooltool-download.sh
+patch_file="$(pwd)/taskcluster/scripts/misc/mingw-winrt.patch"
 
 prepare() {
   mkdir -p $TOOLCHAIN_DIR
@@ -58,6 +59,7 @@ prepare() {
   git clone -n git://git.code.sf.net/p/mingw-w64/mingw-w64
   pushd mingw-w64
   git checkout $mingw_version
+  patch -p1 <$patch_file
   popd
 
   git clone https://github.com/llvm-mirror/libunwind.git