Disable -Werror for a while (for cmake)

Change-Id: I639a043ff24392d85f6ea46eeadf79120dc5fa7d
Reviewed-on: http://review.couchbase.org/28663
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>