Ensure that users and groups are already created when the privileging script
runs. The order these scripts appear in the folded activation-service depends
on the order these services are instantiated in the operating-system.
Fixes <https://issues.guix.gnu.org/73680>.
* gnu/system.scm (operating-system-default-essential-services): Move
privileged-program-service above account-service.
(hurd-default-essential-services): Likewise.
* gnu/tests/base.scm (%activation-os): New variable.
(run-activation-test): New procedure.
(%test-activation): New variable.
Change-Id: I59a191c5519475f256e81bdf2dc4cb01b96c31fe
Signed-off-by: Ludovic Courtès <ludo@gnu.org>