procd: fix compile if procd-ujail is not selected

procd: fix compile if procd-ujail is not selected

Generating syscall-names.h was added as a dependency for ujail in order
to support seccomp for OCI containers.
This, however, slipped into the wrong place and broke cmake in case
of procd-seccomp being selected but procd-ujail not being selected.
Move dependency to the right place to fix that.

Fixes: bb4a446 ("uxc: add container management CLI tool")
Reported-by: Paul Blazejowski <paulb@blazebox.homeip.net>
Signed-off-by: Daniel Golle <daniel@makrotopia.org>