pkg-config file for API option

[roblatham00]

Description

Unify's pkg-config file and unify-config assist with gotcha library approach. Unify needed a pkg-config file for API consumers, too

Motivation and Context

now API consumers, such as ROMIO's configure.ac script, can use pkg-config to find the necessary libraries and flags

How Has This Been Tested?

This commit simplifies ROMIO's configure script and build steps. e benchmarks here. -->

Types of changes

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

[adammoody]

Thanks, @roblatham00 !