portconfigure: Only use the DevSDK if it is present
portconfigure: Only use the DevSDK if it is present

Signed-off-by: Jeremy Huddleston Sequoia <db3cec0cba09acb9cf8fd8bd399a3b27498cf883@macports.org>

danchr/macports-base,neverpanic/macports-base,macports/macports-base,neverpanic/macports-base,danchr/macports-base,macports/macports-base