Adding initial AMReX package (#4467)
Adding initial AMReX package (#4467)

* adding initial amrex package

* adding missing fortran variant predicate

* adjusting description text

* adjusting as per @tgamlin guidance

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