Add a "no suffix" generation in CMake even if MPI is available

[bruno-at-orange]

In conda we do not need the MPI suffixes, and it would simplify the lookup for the executable. At the moment I just rename it after the build.

[bruno-at-orange]

We can easily add a new option in the CMakeFiles.txt e.g. NO_MPI_SUFFIX. But it will introduce an inconsistency in cmake: if NO_MPI_SUFFIX=OFF, cpack will fail with DEB and RPM as it requires now mpi suffixes.
There is perhaps another way: why not use a symlink from MODL to MODL_suffix as it is done with DEB and RPM. Even better we could use cmake install command in conda.

[bruno-at-orange]

Actually, the mpi suffix discovering process fails on conda (all mpi libs are located on the same directory, there is no information about the mpi implementation AFAIK). Then there is no suffix under conda environment. It is more a good side-effect than a feature.

[alexisbondu]

Regarder le lien avec Khiops Env pour une intégration propre dans pyKhiops => simplification possible ?