This commit switches the default repositories to use the build-in
ones from images PR#1112. It is still possible to override using
`/etc/image-builder` and `/usr/share/image-builder` or `--datadir`.
This is implicitly tested via the container test that no longer
includes the files from osbuild-composer in the container.
This commit adds an initial Containerfile to build an `image-builder`
container.
Use all the DNF commands together and add a cleaning command to the end
of it. This makes fewer layers and keeps the image size slightly
smaller.
Co-authored-by: Simon de Vlieger <supakeen@redhat.com>
Signed-off-by: Simon de Vlieger <supakeen@redhat.com>
