releng: Change staging target to use platform integration builds

releng: Change staging target to use platform integration builds

- We need a more recent build of the platfom to fix a dependency
problem (Bug 502114)
- We can now use Apache Derby from Orbit instead of the build server
(Bug 494234)
- There is a new spies plugin that does not depend on JDT which we
can now use (bug 481467).
This plugin contains Sleak (Native handle leak detection) and SWT Spy.

Change-Id: I2bbdd4b287f448150758f6ffca877a8177c8a43c
Signed-off-by: Marc-Andre Laperle <marc-andre.laperle@ericsson.com>
Reviewed-on: https://git.eclipse.org/r/82568
Reviewed-by: Hudson CI
Reviewed-by: Jonathan Rajotte Julien <jonathan.rajotte-julien@efficios.com>
Reviewed-by: Bernd Hufmann <bernd.hufmann@ericsson.com>
Tested-by: Bernd Hufmann <bernd.hufmann@ericsson.com>