i believe i saw a commit message showing julien editted CVSROOT/modules, so you need to do a fresh checkout.
i performed one today and had no issues building the source.
On 3/17, Julien checked in some work in this area. The class is now in common/src/main/org/jboss/nukes/common/ant.
I did a fresh checkout, this is what caused the problem. I will try again.