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

[Andy Kaylor via cfe-commits]

================
@@ -114,10 +114,14 @@ class CIRGenConsumer : public clang::ASTConsumer {
     mlir::MLIRContext &MlirCtx = Gen->getMLIRContext();
 
     if (!FEOptions.ClangIRDisablePasses) {
+      std::string libOptOptions = FEOptions.clangIRLibOptOptions;
+
       // Setup and run CIR pipeline.
-      if (runCIRToCIRPasses(MlirModule, MlirCtx, C,
-                            !FEOptions.ClangIRDisableCIRVerifier,
-                            CGO.OptimizationLevel > 0)
+      const bool enableLibOpt =
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andykaylor wrote:

```suggestion
      const bool EnableLibOpt =
```

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