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

[Hubert Tong via cfe-commits]

================
@@ -0,0 +1,80 @@
+// RUN: %clang_cc1 -triple i686-windows %s -fsyntax-only -Wno-unused-value \
+// RUN:   -Wno-pointer-to-int-cast -Wmicrosoft -verify=ms-anonymous -fms-anonymous-structs
+// RUN: %clang_cc1 -triple powerpc-ibm-aix %s -fsyntax-only -Wno-unused-value \
+// RUN:   -Wno-pointer-to-int-cast -Wmicrosoft -verify=ms-anonymous -fms-anonymous-structs
+// RUN: %clang_cc1 -triple i686-windows %s -fsyntax-only -Wno-unused-value \
+// RUN:   -Wno-pointer-to-int-cast -Wmicrosoft -verify=ms-anonymous -fms-extensions
+// RUN: %clang_cc1 -triple i686-windows %s -fsyntax-only -Wno-unused-value \
+// RUN:   -Wno-pointer-to-int-cast -Wmicrosoft -verify=ms-anonymous -fms-compatibility
+// RUN: %clang_cc1 -triple i686-windows %s -fsyntax-only -Wno-unused-value \
+// RUN:   -Wno-pointer-to-int-cast -Wmicrosoft -verify=ms-anonymous-dis
+// Test that explicit -fno-ms-anonymous-structs does not enable the feature.
+// RUN: %clang_cc1 -triple i686-windows %s -fsyntax-only -Wno-unused-value \
+// RUN:   -Wno-pointer-to-int-cast -Wmicrosoft -verify=ms-anonymous-dis \
+// RUN:   -fno-ms-anonymous-structs
+// Test that explicit -fno-ms-anonymous-structs does not enable the feature.
+// RUN: %clang_cc1 -triple i686-windows %s -fsyntax-only -Wno-unused-value \
+// RUN:   -Wno-pointer-to-int-cast -Wmicrosoft -verify=ms-anonymous-dis \
+// RUN:   -fno-ms-anonymous-structs
----------------
hubert-reinterpretcast wrote:

Remove duplicate test.
```suggestion
// Test that explicit -fno-ms-anonymous-structs does not enable the feature.
// RUN: %clang_cc1 -triple i686-windows %s -fsyntax-only -Wno-unused-value \
// RUN:   -Wno-pointer-to-int-cast -Wmicrosoft -verify=ms-anonymous-dis \
// RUN:   -fno-ms-anonymous-structs
```

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