[clang] [clang] fix uefi target for aarch64 & x86_64 (PR #120632)

[via cfe-commits]

================
@@ -788,16 +789,28 @@ class LLVM_LIBRARY_VISIBILITY ZOSTargetInfo : public OSTargetInfo<Target> {
 // UEFI target
 template <typename Target>
 class LLVM_LIBRARY_VISIBILITY UEFITargetInfo : public OSTargetInfo<Target> {
+  llvm::Triple Triple;
+
 protected:
   void getOSDefines(const LangOptions &Opts, const llvm::Triple &Triple,
-                    MacroBuilder &Builder) const override {}
+                    MacroBuilder &Builder) const override {
+    DefineStd(Builder, "uefi", Opts);
----------------
Prabhuk wrote:

Merged the clean up PR. @petrhosek's thoughts on DefineMacro over DefineStd is sound in my opinion.  Going to merge the predefine PR as well #111719 which we can revert/reland if we have significant push back and deal with it in a way that it doesn't block this PR.

https://github.com/llvm/llvm-project/pull/120632