Update .gitignore to exclude cbcompact wrapper

Change-Id: I3e726f29c76ed0df9c478b8a92d4f1e8a06b35f2
Reviewed-on: http://review.couchbase.org/30161
Reviewed-by: Chiyoung Seo <chiyoung@couchbase.com>
Tested-by: Chiyoung Seo <chiyoung@couchbase.com>