Add spack patch docs to build process section.
Add spack patch docs to build process section.

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