Missing JAR's in Whack

I am relatively new to Java and Ant. I am trying to build Whack, and having issues with missing jars. I added all the jars in in /dist and /merge to the project java build path. Unfortunately the Jetty jar there is missing important stuff, and the package name is wrong for the classes that it does have. So I found the jetty-all jar, and copied it to my hard disk (outside the workspace) and added the jar as an external jar. This resolved all my issues in eclipse, but when I try to run the ant build script (from within eclipse), it is unable to find the jetty classes. I have heard that ant needs to be configured to know where to find the jars as well. Can anyone tell me how to do that?