It is used only in createiso and productimg phases.
For productimg, it needs to be present only when the compose is bootable
and productimg phase is explicitly enabled.
For createiso, it is only needed if runroot is not enabled.
Additionally, if we detect pungi running on arch for which syslinux is
not available, a warning is printed, but the compose is allowed to
continue (and possibly crash later).
Signed-off-by: Lubomír Sedlář <lsedlar@redhat.com>
