[clang] [KeyInstr][Clang] Add Clang option -g[no-]key-instructions (PR #134627)

[Orlando Cazalet-Hyams via cfe-commits]

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@@ -4767,6 +4767,13 @@ renderDebugOptions(const ToolChain &TC, const Driver &D, const llvm::Triple &T,
       CmdArgs.push_back("-gembed-source");
   }
 
+  if (Args.hasFlag(options::OPT_gkey_instructions,
+                   options::OPT_gno_key_instructions, false)) {
+    CmdArgs.push_back("-gkey-instructions");
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OCHyams wrote:

We can ditch the `-mllvm` soon as it was mostly a convenience for development. I don't have a pull request yet that implements the necessary changes but plan to soon (such changes will necessary for bitcode handling, so that's not a nebulous soon).

It would be preferable to me if we can keep it temporarily (land this as is), if that's not a problem.

https://github.com/llvm/llvm-project/pull/134627