- use orte-info to determine prefix/libdir for openmpi.
This removes a run-time dependency on mpicc, which is actually
only needed for building with MPI (not running with MPI).
The corresponding openmpi devel package (deb/rpm) will not
necessarily be installed on a particular system.
- retain mpicc logic if the new logic using orte-info does not
deliver an answer. Final fallback to using 'orterun' to
infer prefix/libdir.
- Additional logic for intel and msmpi to make it easier to
locate these vendor packages within ThirdParty
(ie, under ThirdParty/opt/...)
CONFIG: improve robustness
- add check for absolute path when adding PATH/LD_LIBRARY_PATH etc.
- prefix more variables with '_foam*' to prevent accidental overwrite
of userspace shell variables when sourcing