[clang] [Clang] Add clang flag --cstdlib (PR #183254)

[via cfe-commits]

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@@ -194,6 +194,7 @@ class ToolChain {
   mutable std::optional<CXXStdlibType> cxxStdlibType;
   mutable std::optional<RuntimeLibType> runtimeLibType;
   mutable std::optional<UnwindLibType> unwindLibType;
+  mutable std::optional<std::string> cstdlibType;
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quic-k wrote:

@voltur01 
do you prefer enums over a string here, considering above points?
since you will using this flag too

https://github.com/llvm/llvm-project/pull/183254