gfortran 10 vs mpi vs c++ vs probably something else as well

[cyrush]

gfortran 10 started being very picky about type matching, which impacts mpi function call interfaces.

By default the type mismatch issues aren't warnings - they are errors. So it impacts existing, working fortran mpi codes.

mpich wrappers have started to add the compile flags to avoid errors (a better state)

BLT's mpi support does not separate the fortran and c++ compiler flags. That leads to warnings b/c the fortran compiler flags are passed to the c++ compiler. (not a big issue, but creates a lot of noise)

https://github.com/Alpine-DAV/ascent/issues/727