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

[Joseph Huber via cfe-commits]

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@@ -790,7 +790,9 @@ template <typename Target>
 class LLVM_LIBRARY_VISIBILITY UEFITargetInfo : public OSTargetInfo<Target> {
 protected:
   void getOSDefines(const LangOptions &Opts, const llvm::Triple &Triple,
-                    MacroBuilder &Builder) const override {}
+                    MacroBuilder &Builder) const override {
+    Builder.defineMacro("__UEFI__");
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jhuber6 wrote:

I wonder if this should be consistent with the Unix flavors, I don't know what the UEFI target does or if GCC or another other compiler already has a macro for this.
```suggestion
    DefineStd(Builder, "uefi", Opts);
```

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