Fixes to enable running on OLCF Crusher/Frontier

[MichaelBrim]

Description

A handful of minor fixes over v1.0 to overcome build and run issues on OLCF Crusher/Frontier:

• Use SLURM srun --overlap to run unifyfsd on same CPU/socket as an application
• Only link the MPI UnifyFS client libraries against MPI

Also includes a couple of improvements to help users build with Unify:

• Updated pkg-config support to properly handle our margo dependency, and added a new unifyfs-static.pc for builds that want to use linker wrapping
• A new standalone Makefile.examples that can be used to build the example programs from an installed Unify (using the improved pkg-config support). This works around an issue where our MPI wrapper support is broken when linked using the standard build's libtool-based method and Cray PE.

How Has This Been Tested?

Tested using Unify examples on Crusher with up to 32 processes-per-node.

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Performance enhancement (non-breaking change which improves efficiency)
• [x] Code cleanup (non-breaking change which makes code smaller or more readable)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] Testing (addition of new tests or update to current tests)
• [ ] Documentation (a change to man pages or other documentation)

Checklist:

• [x] My code follows the UnifyFS code style requirements.
• [ ] I have updated the documentation accordingly.
• [x] I have read the CONTRIBUTING document.
• [ ] I have added tests to cover my changes.
• [x] All new and existing tests passed.
• [x] All commit messages are properly formatted.