MB-10793: Copy couchdb.plt to build/couchdb to save build time

Change-Id: Ie235a40d00becc23925f9b960b360d37fceedaa3
Reviewed-on: http://review.couchbase.org/35483
Reviewed-by: Eric Limare <eric.limare@couchbase.com>
Tested-by: Eric Limare <eric.limare@couchbase.com>