Changes to build GPU-version of Exa with HYPRE and CSG on Perlmutter.

Bhargav Sriram Siddanirequested to merge
bsiddani/docs:perlmutter_hypre_update into main

The following changes suggested by Aashish Goyal were required to compile GPU-version of Exa with HYPRE and CSG on Perlmutter.

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