They're not handled by the current 7z version under MSW if the user
doesn't have administrative rights and, instead of dealing with this,
it's simpler to just never include any symlinks in the archives as we
don't really need them anyhow.
So add a check ensuring that no symlinks are included in the
distribution archives to avoid more problems such as the one fixed in
the parent commit in the future.
f2425c5cbd