- no limit to the number of ways of filing ptscotch libraries.
RedHat/Fedora/CentOS should look for these directories:
ptscotch include=/usr/include/openmpi-x86_64
ptscotch library=/usr/lib64/openmpi/lib
when MPI_ARCH_PATH=/usr/lib64/openmpi
and mpicc --showme:compile yields -I/usr/include/openmpi-x86_64