[clang] [CIR][OpenMP] Implement lowering for the 'if' clause for 'parallel' d… (PR #204999)

[Sergio Afonso via cfe-commits]

================
@@ -84,3 +84,75 @@ void proc_bind_parallel() {
   // CHECK-NEXT: omp.terminator
   // CHECK-NEXT: }
 }
+
+void if_parallel() {
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skatrak wrote:

Nit: We should have a case where an inapplicable `if` condition is passed, like:
```c++
#pragma omp parallel if (simd: validCondition)
{}
```
And check that no `if` clause was added to the `omp.parallel` operation.

https://github.com/llvm/llvm-project/pull/204999