How can I easily set (back) bundled JRuby interpreter?

NetBeans IDE 6.1

Choose Tools > Ruby Platforms from the main toolbar and select Built-in JRuby from the Platforms list.

To change the platform for a specific project, right-click the project's node and choose Properties. Select the Ruby Platform from the drop-down list.

NetBeans IDE 6.0

In the Ruby Options (Tools | Options | Ruby) delete the text in the Ruby Interpreter textfield and hit OK.