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

[kadir çetinkaya via cfe-commits]

================
@@ -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<["--"],
----------------
kadircet wrote:

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

Oh didn't notice we actually had "lexical" sections in the doc (AFAICT it doesn't have any semantic affect afterwards, flag is still only visible for cc1 and clang-driver).

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

Going to carry this discussion into RFC to make sure it doesn't get lost. https://discourse.llvm.org/t/rfc-add-support-for-controlling-diagnostics-severities-at-file-level-granularity-through-command-line/81292/21?u=kadircet

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