[flang] [llvm] Revert "Revert "[flang][openmp] Adds Parser and Semantic Support for Interop Construct, and Init and Use Clauses."" (PR #132343)

[Kiran Chandramohan via llvm-commits]

kiranchandramohan wrote:

> I have added `%openmp_flags` on `Lower/OpenMP/Todo/inteorp-construct.f90`.
> 
> `Parser/OpenMP/interop-construct.f90` and `Semantics/OpenMP/interop-construct.f90` already has `-fopenmp` as a parameter in the command. But if you want me to add `%openmp_flags` instead of -fopenmp, happy to do so!
> 
> Thanks!

`-fopenmp` is not sufficient. `%openmp_flags` expands to the following:
```
# Determine if OpenMP runtime was built (enable OpenMP tests via REQUIRES in test file)
if config.have_openmp_rtl:
    config.available_features.add("openmp_runtime")
    # For the enabled OpenMP tests, add a substitution that is needed in the tests to find
    # the omp_lib.{h,mod} files, depending on whether the OpenMP runtime was built as a
    # project or runtime.
    if config.openmp_module_dir:
        config.substitutions.append(
            ("%openmp_flags", f"-fopenmp -J {config.openmp_module_dir}")
        )
    else:
        config.substitutions.append(("%openmp_flags", "-fopenmp"))
 ```

https://github.com/llvm/llvm-project/pull/132343