Running ant tar produces a very small tar file because all .jar dependencies are missing. This happens since the switch to Ivy.
Adding common.ivy.lib.dir to the build.xml fixes some of it but some things still don't work:
The jars for the contrib apps still seem to be missing. At the moment this is only stargate but the I've got the same problem for the new thrift contrib. I am afraid I don't know enough about Ant or Ivy to be of any further assistance.