package/systemd: needs timezone info

systemd does not like being booted without any timezone info (especially
on a R/O filesystem), so we forcibly enable that.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Maxime Hadjinlian <maxime.hadjinlian@gmail.com>
[Thomas: fix alphabetic ordering.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>