[clang] [Clang][OpenMP] Only defer loop analysis in a dependent context (PR #226805)

[Oliver Hunt via cfe-commits]

https://github.com/ojhunt requested changes to this pull request.

In the earlier iteration the llm added a block test, and didn't indicate why. I investigated and found _many_ problems around blocks and omp, but I think there's something weird happening in dependent blocks in general.

But I looked into lambdas as well and with this PR we now get incorrect codegen:

```cpp
int foo(auto x, int(*F)() = []()->int{
  int k = 0;
  #pragma omp simd collapse(sizeof(x)/sizeof(x))
  for (int i = 0; i < 10; ++i)
    k++;
  return k; }) {
return F();
}
int bar() { return foo(1); }
```

This drops the for loop and reduces to `ret 0`.

The original version of this  `#pragma omp simd collapse(sizeof(x))` which should produce an error, but also just drops the loop.

I think this PR is tending towards addressing symptoms 


https://github.com/llvm/llvm-project/pull/226805