MB-9590 Set library path for MacOSX

Unfortunately it the runtime linker on MacOSX don't work
the same way as on our other platforms..

Change-Id: Ibe41018ce29e2fa87098887f9ee6728167d993c1
Reviewed-on: http://review.couchbase.org/30400
Reviewed-by: Michael Wiederhold <mike@couchbase.com>
Tested-by: Michael Wiederhold <mike@couchbase.com>