Clang has better detection for unused vars when using auto cleanup
functions. We should eventually just fold this back into the first
testsuite. But let's just turn it on for now, at least until it's
satisfied with the whole codebase.
Closes: #549
Approved by: cgwalters
Add a YAML file for the new Red Hat CI framework.
Rather than re-installing all the build deps everytime, which takes
time, I added a Dockerfile that we can wire up to the Docker Hub. For
now it lives at `jlebon/ostree-tester:rhci`, but we can move it under
the `projectatomic` org (or a new `ostree` org).
Closes: #535
Approved by: cgwalters