Enhance MPI support in molpro.py.

[akesandgren]

Don't touch the LAUNCHER, the default works as is and the old replacement code broke the code since it changed multiple LAUNCHER instances. Also reduce optimization to -O2, intel coredumps on some files. Finally turn on VERBOSE builds.

[ocaisa]

What is the LAUNCHER default? Unless it is srun on JURECA it won't work.

[akesandgren]

The default is mpirun which normally works on slurm based systems.

But if that is an actual problem then that part of the code has to be rewritten a lot more carefully anyway. The code before this PR breaks things.

Anyway the previous code only changed it temporarily to the launcher determined by toolchain.mpi_cmd_for for usage during building of molpro.

[akesandgren]

@ocaisa Do you have a possibility of testing this on JURECA?

[akesandgren]

@boegel @ocaisa This could use a retest from you

[akesandgren]

@ocaisa still need a re-test from JURECA on this...

[ocaisa]

@akesandgren Don't hold this back for a test from me, mpirun is not going to work at JSC but that's no reason to leave something broken in place.

[akesandgren]

In that case we need someone to review this, @boegel ??