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>