hypre: make mpi dependency optional (#5905)
hypre: make mpi dependency optional (#5905)


LLNL/spack,iulian787/spack,skosukhin/spack,tmerrick1/spack,lgarren/spack,mfherbst/spack,tmerrick1/spack,LLNL/spack,EmreAtes/spack,skosukhin/spack,tmerrick1/spack,krafczyk/spack,matthiasdiener/spack,lgarren/spack,LLNL/spack,LLNL/spack,mfherbst/spack,matthiasdiener/spack,mfherbst/spack,skosukhin/spack,tmerrick1/spack,krafczyk/spack,lgarren/spack,skosukhin/spack,lgarren/spack,iulian787/spack,iulian787/spack,matthiasdiener/spack,skosukhin/spack,mfherbst/spack,krafczyk/spack,krafczyk/spack,iulian787/spack,iulian787/spack,EmreAtes/spack,krafczyk/spack,tmerrick1/spack,lgarren/spack,EmreAtes/spack,EmreAtes/spack,EmreAtes/spack,LLNL/spack,matthiasdiener/spack,matthiasdiener/spack,mfherbst/spack