package/systemd: disable zstd for host-systemd

systemd 246 added support for zstd compression of large fields in
journal files [1]. Since zstd is only used at runtime, we don't
need it to enable its support in host-systemd.

[1] https://github.com/systemd/systemd/blob/v246/NEWS#L323-L331



Signed-off-by: Titouan Christophe <titouan.christophe@railnova.eu>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>