The Ant Platform project is run the same way as the Debug Platform project.

To get started, follow the instructions specified in the "Contributing to the Debug Platform" document.

NOTE: The Debug Platform instructions for setting up a selfhosting workspace tell you how to check the Debug Platform projects out of CVS. To work with the Ant Platform projects, check out the following projects instead:
  org.apache.ant
  org.eclipse.ant.core
  org.eclipse.ant.ui
  org.eclipse.ui.externaltools
  org.eclipse.ant.tests.core (optional)
  org.eclipse.ant.tests.ui (optional)