[clang] [clang][driver] Add -mtls-dialect option (PR #79031)

[Fangrui Song via cfe-commits]

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@@ -72,6 +72,11 @@ class CodeGenOptions : public CodeGenOptionsBase {
     LocalExecTLSModel
   };
 
+  enum TLSDialect {
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MaskRay wrote:

Prefer enum class (I think it has been more popular in other parts of Clang, perhaps CodeGen/Sema). `TLSDialect::TraditionalDynamic` and `TLSDialect::TLSDesc`

https://github.com/llvm/llvm-project/pull/79031