[clang] [Clang][Xtensa] Add Xtensa target. (PR #118008)

[Eli Friedman via cfe-commits]

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@@ -9727,6 +9727,51 @@ static TypedefDecl *CreateHexagonBuiltinVaListDecl(const ASTContext *Context) {
   return Context->buildImplicitTypedef(VaListTagArrayType, "__builtin_va_list");
 }
 
+static TypedefDecl *
+CreateXtensaABIBuiltinVaListDecl(const ASTContext *Context) {
+  // typedef struct __va_list_tag {
+  RecordDecl *VaListTagDecl;
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efriedma-quic wrote:

```suggestion
  RecordDecl *VaListTagDecl = Context->buildImplicitRecord("__va_list_tag");
```

https://github.com/llvm/llvm-project/pull/118008