[clang] [flang] Add IR Profile-Guided Optimization (IR PGO) support to the Flang compiler (PR #136098)

[Tom Eccles via cfe-commits]

================
@@ -909,6 +940,29 @@ void CodeGenAction::runOptimizationPipeline(llvm::raw_pwrite_stream &os) {
   llvm::PassInstrumentationCallbacks pic;
   llvm::PipelineTuningOptions pto;
   std::optional<llvm::PGOOptions> pgoOpt;
+ 
+  if (opts.hasProfileIRInstr()){
+    // // -fprofile-generate.
----------------
tblah wrote:

```suggestion
    // -fprofile-generate.
```

https://github.com/llvm/llvm-project/pull/136098