org.aspectj/lib/ant/aspectj-ant-readme.txt

The AspectJ tree builds using Ant 1.6.3.  
(No longer is a special version of Ant required.)

To run tests using the junit task, junit.jar is added to lib/.

This directory contains:

o The contents of the binary distribution of Ant 1.6.3,
  not including the docs directory.

o ant-src.zip, .java extracted from the source distribution of Ant 1.6.3.

For Ant, see http://ant.apache.org.