If the OpenMPI build finds the infiniband drivers in /usr/lib64, it adds
-Wl,-rpath -Wl,/usr/lib64 to the OpenMPI wrappers. If the wrappers are using
a compiler outside of /usr, and the OpenMPI wrappers are used to build software
outside of Spack, they will rpath /usr/lib64 into the executable which then has
GLIBC, GLIBCXX runtime errors due to it picking up GCC libraries in /usr/lib64.
This adds the directories specified in "extra_rpaths" to the OpenMPI wrappers,
which allows them to use the correct compiler when invoked outside of Spack
builds.
15d96f0166