sourceballs: fix ACL issues on nymeria

ACLs from the WORKDIR were used, leading to problems as these weren't
world-readable. Fix follows ftpdir-cleanup.

Signed-off-by: Jan Alexander Steffens (heftig) <jan.steffens@gmail.com>
Signed-off-by: Pierre Schmitz <pierre@archlinux.de>
Add lastupdate file

This allows for faster checking if an update might be needed and helps
to let reporead run when something changed.

Signed-off-by: Florian Pritz <bluewind@xinu.at>