Mute output from make unless told to be verbose

Change-Id: Iea4d43744460b61183f399e885480d46a790d9a3
Reviewed-on: http://review.couchbase.org/34011
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Iryna Mironava <irynamironava@yandex.ru>