systemd: Expose resolv-conf alternative only when resolved is built
When systemd is built without internal resolver, it does not make
sense to expose it as a resolv-conf alternative and can even break
images where this alternative would be chosen, because of an
invalid symlink.
Signed-off-by: Alexandre Bard <alexandre.bard@netmodule.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>