[clang] [Clang] Improve infrastructure for libstdc++ workarounds (PR #141977)

[Erich Keane via cfe-commits]

================
@@ -129,6 +129,12 @@ enum class EmbedResult {
   Empty = 2,    // Corresponds to __STDC_EMBED_EMPTY__
 };
 
+struct CXXStandardLibraryVersionInfo {
+  enum Library { Unknow, LibStdCXX };
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erichkeane wrote:

```suggestion
  enum Library { Unknown, LibStdCXX };
```


https://github.com/llvm/llvm-project/pull/141977