ant-1.5.3-1-src.tar.bz2 is not available from archive.apache.org or other mirrors...it's only offered as a ZIP archive for some strange reason. Make sure you have emerged unzip (maybe editing the ebuild dependencies would take care of this) and change the SRC_URI line near the top of the ebuild to read as follows: SRC_URI="mirror://apache/ant/source/apache-${PN}-${PV}-1-src.zip" (I found this while setting up PostgreSQL on a new server from the stage3 i686 tarball...maybe unzip is in some of the other stage3s. If it isn't, it should be added.)
This is now fixed. Thanks Spanky !!