wi4mpi command doesn't work with different installations of MPI

[laurent-nguyen]

See with OpenMPI and IntelOneAPI, it seems wi4mpi command set paths (with lib or lib64). But, the MP installations can be different along the way there are packaged (manually compiled or Fedora packaging for example).

I suggest to detect if ${MPI_ROOT}/lib/libmpi.so does exist, otherwise try with ${MPI_ROOT}/lib64/libmpi.so.

[adrien-cotte]

Obviously... Thanks for your feedback!

[kevin-juilly]

In Fedora (and other Red Hat related distribution), the lib64 is part of the prefix (/usr/lib64/openmpi).
If someone manually compiles an mpi and does not use ${MPI_ROOT}/lib, they probably overrided libdir at configure time. It means it can be anything so it's on them to properly export WI4MPI_RUN_* variables.

But I still did the work, refactoring the script as a bonus.