Ok, I fixed the problem, the latest change made on the aop/build.xml (31-12-2006) makes the build fails when building a recent checked out jbossaop project, because it can't find some files/directories
To fix it I had to create :
aop/output/etc/default.mf aop/output/etc aop/output/lib
maybe adding a dependency at the source-jar in aop/build.xml target could solve this problem, I will look for it.
I have fixed the build.