[clang] [clang][Sema] Fix ObjC file-scope literal diagnostic under -fobjc-arc (PR #209688)

[Aaron Ballman via cfe-commits]

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+// RUN: %clang_cc1 -fsyntax-only -triple x86_64-apple-macosx11.0.0 -fobjc-runtime=macosx-11.0.0 -fobjc-constant-literals -fconstant-nsnumber-literals -fconstant-nsarray-literals -fconstant-nsdictionary-literals -verify %s
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AaronBallman wrote:

Can you add an `-x objective-c++` RUN line as well? There are file scope initialization differences between C and C++ so the goal is to make sure that we get the C++ behavior in Objective-C++ mode instead of the C behavior.

https://github.com/llvm/llvm-project/pull/209688