SelectionScriptLinker was setting the wrong timestamp on
the generated selection script when used in production mode.
It mistakenly thought it was in dev mode.

Review at http://gwt-code-reviews.appspot.com/287801

Review by: scottb@google.com

git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@7824 8db76d5a-ed1c-0410-87a9-c151d255dfc7