CBLT-319:  windows sync_gateway packages have different prefix

Change-Id: Icb2adea495cb5a20b94fa09e34ad2c5fec88b9e6
Reviewed-on: http://review.couchbase.org/38577
Reviewed-by: Philip Labee <philip@couchbase.com>
Tested-by: Philip Labee <philip@couchbase.com>