Introduce a new `tar` option, which when given together with the
required `tar.filename` option, will result in the output of the
assembler being a tarball that contains the repo and the compose
information (`compose.json`).
Requires the `tar` command to be present in the build root. Modify
the sample to use that option and include the tar for the build
pipeline.
This converts all fedora links in our samples to `mirrors.kernel.org`.
This mirror works best from around the world, so lets avoid the wild
mix of local mirrors and instead use kernel.org.
This mirror is also well-managed and properly funded, so we should not
run into too many problems with it.
This is a Fedora 31 based example that results in a ostree repo
with a ostree commit. The latter was composed from the file system
tree that was created via the given osbuild stages.
