[clang] [CIR] Intitial upstreaming of LibOpt pass (PR #172487)

[Andy Kaylor via cfe-commits]

================
@@ -3253,6 +3253,14 @@ def clangir_disable_verifier : Flag<["-"], "clangir-disable-verifier">,
   HelpText<"ClangIR: Disable MLIR module verifier">,
   MarshallingInfoFlag<FrontendOpts<"ClangIRDisableCIRVerifier">>;
 
+def fclangir_lib_opt_EQ : Joined<["-"], "fclangir-lib-opt=">,
+  Visibility<[ClangOption, CC1Option]>, Group<f_Group>,
+  HelpText<"Enable C/C++ library based optimizations (with options)">,
+  MarshallingInfoString<FrontendOpts<"clangIRLibOptOptions">>;
+def fclangir_lib_opt : Flag<["-"], "fclangir-lib-opt">,
+  Visibility<[ClangOption, CC1Option]>, Group<f_Group>,
+  Alias<fclangir_lib_opt_EQ>, AliasArgs<[""]>,
----------------
andykaylor wrote:

```suggestion
  Alias<fclangir_lib_opt_EQ>,
```
When I build this PR locally, the lib-opt.cpp test is failing with a message saying, "AliasArgs should be either 0 or non-empty." I don't think you want it here.

https://github.com/llvm/llvm-project/pull/172487