[clang] [clang-tools-extra] [llvm] [clang] Introduce diagnostics suppression mappings (PR #112517)

[Aaron Ballman via cfe-commits]

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@@ -9017,3 +9017,8 @@ def wasm_opt : Flag<["--"], "wasm-opt">,
   Group<m_Group>,
   HelpText<"Enable the wasm-opt optimizer (default)">,
   MarshallingInfoNegativeFlag<LangOpts<"NoWasmOpt">>;
+
+def warning_suppression_mappings_EQ : Joined<["--"],
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AaronBallman wrote:

This should move elsewhere in Options.td, it's currently listed under `clang-dxc` options.

Also, should this be exposed in clang-cl as well? What about flang? CC @zmodem @rnk @MaskRay @jansvoboda11 for opinions

https://github.com/llvm/llvm-project/pull/112517