Add NREL's Kestrel CPU build files

[R1j1t]

These changes add Kestrel (NREL) specific build files. Not sure if there is any test files which can be added.
@rk-lindsey @nirgoldman

• Requested develop as target branch
• Attached test suite log file
• Alerted reviewers if edits impact CMake or Makefile files

[rk-lindsey]

Hi @R1j1t, this PR generally looks good. However, we've recently updated our repository to use a more modern version of LAMMPS.

Hence, please update your fork (see the screenshot below) to get the latest changes and confirm that:

• There are no merge conflicts
• The makefile/install.sh edits work as expected.

[R1j1t]

Thanks @rk-lindsey for reviewing the PR. I am excited for the new release, and will update my branch by next week. Currently I am trying to make intel modules work, which are apparently faster than mpich.