Add a test runner that builds with MUSL libc

[chucklever]

Recent issues have demonstrated that ktls-utils has not built on MUSL libc-based systems, maybe since day zero. Let's see if there is a GitHub Action configuration that provides a MUSL-based platform for build testing.

[chucklever]

The oracle/ project's security settings might prevent the use of non-blessed Actions, meaning we are forced to stick with Actions and steps provided by GitHub, not by 3rd parties.