[clang] [Frontend][Sema] Add CC1-only -fms-anonymous-structs to enable Microsoft anonymous struct/union feature (PR #176551)

[Hubert Tong via cfe-commits]

================
@@ -25,6 +25,7 @@
 
 // This needs to exit non-0, for configure scripts.
 // RUN: not %clang /GR-
+// RUN: not %clang %s -fms-anonymous-structs -### 2>&1 | FileCheck %s --check-prefix=CL-MS-ERROR
----------------
hubert-reinterpretcast wrote:

I don't think updating this test is necessary. It is not commonly updated when new options are added.

https://github.com/llvm/llvm-project/pull/176551