Use compose-utils to copy variants into public location
This requires compose-utils >= 0.1.7.
Currently only primary architectures are composed based on this config.
Once other arches are added, they can be filtered with `--arch` option.
To debug what will happen when the command is run, add `--dry-run`. It
will print the exact rsync commands that would be used. Appending `--
--dry-run` at the end of the command will pass the option to rsync and
give different debugging information.
Signed-off-by: Lubomír Sedlář <lsedlar@redhat.com>