Pass through PRODUCT_VERSION

Change-Id: Ia2576b4b449393c9649437ef6020d716fbdcc8c6
Reviewed-on: http://review.couchbase.org/35420
Reviewed-by: Eric Limare <eric.limare@couchbase.com>
Reviewed-by: Chris Hillery <ceej@couchbase.com>
Tested-by: Chris Hillery <ceej@couchbase.com>