jenkins/war/resources/help/project-config/ant.html

<div>
  For projects that use Ant as the build system. This causes Hudson to
  invoke Ant with the given targets and options. Any non-zero exit code 
  causes Hudson to mark the build as a failure.
  <p>
  Hudson supplies some <a href='../../env-vars.html' target=_new>
  environment variables</a> that can be used from within the build script.
</div>