Use the tar Posix option for tarballs
    
    This is necessary to be able to successfully build archives in
    environments controlled by an IPA domain which may have large uidNumbers
    for user accounts.
    
    tar-ustar allows UID/GID numbers only up to 2 million and by default a
    new IPA installation can assigne UIDs in the billion range.
    
    https://fedorahosted.org/freeipa/ticket/6418
    
    Signed-off-by: Simo Sorce <simo@redhat.com>
    Reviewed-By: Petr Spacek <pspacek@redhat.com>