[clang] NFC, avoid create a new FunctionTypeInfo object in the function call.

FunctionTypeInfo is a large object, no need to create a new one for this case.

Author: hokein

clang/lib/Parse/ParseDecl.cpp

@@ -676,7 +676,7 @@ void Parser::ParseGNUAttributeArgs(
   std::optional<ParseScope> PrototypeScope;
   if (normalizeAttrName(AttrName->getName()) == "enable_if" &&
       D && D->isFunctionDeclarator()) {
-    DeclaratorChunk::FunctionTypeInfo FTI = D->getFunctionTypeInfo();
+    const DeclaratorChunk::FunctionTypeInfo& FTI = D->getFunctionTypeInfo();
     PrototypeScope.emplace(this, Scope::FunctionPrototypeScope |
                                      Scope::FunctionDeclarationScope |
                                      Scope::DeclScope);