Fixed android build to work multithreaded.

Fixed android build to work multithreaded.

Previously the android build was missing proper dependencies
so could only be built if multithreading was disabled. This change
adds minimal dependencies to get gradle to be executed after the
native parts are built, and re-enables threaded builds.

This could reduce build times by roughly 75% on average systems.

Signed-off-by: Jon A. Cruz <jonc@osg.samsung.com>
Change-Id: Iccecd7cc976855592d3375027a4de1f9fd2dbe98
Reviewed-on: https://gerrit.iotivity.org/gerrit/2310
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Tim Kourt <tim.a.kourt@intel.com>