Don't build _d suffix for tools on non-windows platforms

Change-Id: Idac3bd355ad0edddc1683cd64001733f7ce90bfd
Reviewed-on: http://review.couchbase.org/41656
Tested-by: Mark Nunberg <mnunberg@haskalah.org>
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>