OpenMP option for Cray is -fopenmp

Cray is a clang based compiler (at least for C C++). It uses -fopenmp to enable OpenMP.

Yet, FindOpenMP.cmake 3.27 mention:

    # Cray compiler activate OpenMP with -h omp, which is enabled by default.                                                                                                                
    set(OMP_FLAG_Cray " " "-h omp")


The newer Cray compiler is Clang-based, but the older one is not. FindOpenMP needs to learn this distinction. Can you please file an issue about this and include compiler details (version info, etc.).

I see CMake Issue 25100 for this, thanks.