add workflow for Mac OS builds

[rem1776]

Description
adds a workflow to build on Mac OS using cmake, gnu15, and openmpi.

I have it set up to test the build when merged into main. Unit tests are skipped because they are failing, so this is just to ensure it can build.

this also fixes a bug in the cmake build with the libyaml include path not being used.

Thanks @ilaflott for finding the right gcc!

How Has This Been Tested?
CI

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules
• New check tests, if applicable, are included
• make distcheck passes