Ant upstream authors recommend using classpath attribute for optional ant tasks when defining the task in build.xml.[1] Hence the symlink should not be present in ant's library. Also the symlink modifies the default classpath of ant which will cause problem if user wants to use another version of ivy outside the system installation.
[1] http://ant.apache.org/manual/install.html#optionalTasks -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org