Fixes <https://bugs.gnu.org/40839>.
Reported by Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
Fix suggested by Mathieu Othacehe <m.othacehe@gmail.com>
However, <https://bugs.gnu.org/29296> still applies; %current-target-system
may not be bound.
* gnu/services/shepherd.scm (scm->go): Use `with-target' when cross-compiling.