CBD-1400:  fix up copy of EXE to destination for windows TOY builders

Change-Id: If9ab697598a0187cdd1bfb7c71fde73b9f924693
Reviewed-on: http://review.couchbase.org/39858
Reviewed-by: Philip Labee <philip@couchbase.com>
Tested-by: Philip Labee <philip@couchbase.com>