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

[Hubert Tong via cfe-commits]

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@@ -350,6 +350,9 @@
 // WJoined: "-cc1"
 // WJoined: "-Wunused-pragmas"
 
+// RUN: %clang_cl -c -fms-extensions -### -- %s 2>&1 | FileCheck -check-prefix=CHECK-MS-ANON-STRUCT %s
+// CHECK-MS-ANON-STRUCT: "-fms-extensions" "-fms-anonymous-structs"
+
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hubert-reinterpretcast wrote:

@riyaz86a, please remove this driver test too.

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