Make demo_nodes_cpp_native install stuff only when it builds (#590)
Make demo_nodes_cpp_native install stuff only when it builds (#590)

* Make demo_nodes_cpp_native install stuff only when it builds

Signed-off-by: Shane Loretz <7fde345e8e2e22c78a1570a4807e4629866dc7de@osrfoundation.org>

* doing nothing -> skipping

Signed-off-by: Shane Loretz <7fde345e8e2e22c78a1570a4807e4629866dc7de@osrfoundation.org>

Signed-off-by: Shane Loretz <7fde345e8e2e22c78a1570a4807e4629866dc7de@osrfoundation.org>
ros2/demos,ros2/demos,ros2/demos,ros2/demos