openmpi: add Fortran support for MIPS64

openmpi: add Fortran support for MIPS64

We include a file containing cached values for Fortran tests that are
performed at the configure step. These tests fail when cross-compiling
and this is known upstream. See:

https://www.open-mpi.org/community/lists/users/2013/01/21186.php

In that thread the upstream maintainer admits that "cross compiling
OpenMPI is a known issue" and the way to workaround this is to
"pre-populate configure's answers to the Fortran tests (so that it
doesn't actually have to run anything)"

Signed-off-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
[Thomas: use a config cache.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>