[clang] Try to fix builders

Try to fix these errors:

SemaDeclCXX.cpp:16666:19: error: declaration of ‘const clang::Expr* clang::Sema::DiagnoseStaticAssertDetails(const clang::Expr*)::<unnamed struct>::Expr’ changes meaning of ‘Expr’ [-fpermissive]
16666 |       const Expr *Expr;
      |                   ^~~~

clang/lib/Sema/SemaDeclCXX.cpp

@@ -16663,7 +16663,7 @@ void Sema::DiagnoseStaticAssertDetails(const Expr *E) {
       return;
 
     struct {
-      const Expr *Expr;
+      const clang::Expr *Expr;
       Expr::EvalResult Result;
       SmallString<12> ValueString;
       bool Print;