Bug 1494384 - fix aarch64 __va_start checking in clang; r=dmajor

We need this so we can get a libclang to use for AArch64 bindgen.

build/build-clang/aarch64-vastart-checking.patch

@@ -0,0 +1,16 @@
+AArch64 Windows uses a five-argument __va_start, just like ARM.
+
+https://bugs.llvm.org/show_bug.cgi?id=39090
+
+diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
+index 22483f8..53d9cb2 100644
+--- a/clang/lib/Sema/SemaChecking.cpp
++++ b/clang/lib/Sema/SemaChecking.cpp
+@@ -917,6 +917,7 @@ Sema::CheckBuiltinFunctionCall(FunctionDecl *FDecl, unsigned BuiltinID,
+     switch (Context.getTargetInfo().getTriple().getArch()) {
+     case llvm::Triple::arm:
+     case llvm::Triple::thumb:
++    case llvm::Triple::aarch64:
+       if (SemaBuiltinVAStartARMMicrosoft(TheCall))
+         return ExprError();
+       break;

build/build-clang/clang-win32-st-an.json

@@ -16,6 +16,7 @@
       "r318309.patch",
       "r320462.patch",
       "msvc-host-x64.patch",
+      "aarch64-vastart-checking.patch",
       "loosen-msvc-detection.patch"
     ]
 }

build/build-clang/clang-win64-st-an.json

@@ -18,6 +18,7 @@
       "r320462.patch",
       "r327876.patch",
       "loosen-msvc-detection.patch",
+      "aarch64-vastart-checking.patch",
       "fflush-before-unlocking.patch"
     ]
 }

build/build-clang/clang-win64.json

@@ -18,6 +18,7 @@
       "r342649-hotpatch-8-byte-nops.patch",
       "r342652-unpoison-thread-stacks.patch",
       "r343123-pin-asan-dll.patch",
+      "aarch64-vastart-checking.patch",
       "loosen-msvc-detection.patch"
     ]
 }