fortran vs mpi logic

[cyrush]

Use case:

Fortran language support is on - but MPI Fortran support is not needed.

I think because BLT calls find_package(MPI REQUIRED) we will always hit an error:

  49    -- Found MPI_C: /lib64/libxpmem.so (found version "3.1")
     50    -- Found MPI_CXX: /lib64/libxpmem.so (found version "3.1")
     51    -- Could NOT find MPI_Fortran (missing: MPI_Fortran_WORKS)
  >> 52    CMake Error at /usr/tce/backend/installations/linux-rhel8-x86_64/gcc
           -8.3.1/cmake-3.24.2-ywx52e32uh6gkxzuyubpwkulzgdvxyh6/share/cmake-3.2
           4/Modules/FindPackageHandleStandardArgs.cmake:230 (message):
     53      Could NOT find MPI (missing: MPI_Fortran_FOUND) (found version "3.
           1")

For this case, the following would work:

find_package(MPI COMPONENTS C)

But we need to find the right way to wire as a blt option.