dnsmasq: fix parallel make failure

The dnsmasq target depends on .configured and $(objs). .configured does an rm
-f *.o. Yet the only thing telling make to build the .configured target before
the $(objs) target was the order of the dependencies of the dnsmasq target. We
can't rely on that order when doing a paralllel make build, so add an explicit
rule to enforce that order.

JIRA: SB-2767

Signed-off-by: Christopher Larson <kergoth@gmail.com>
Merge pull request #186 from kergoth/sb-2767

dnsmasq: fix parallel make failure