JIRA 4.1 breaks the instructions on customising the Bugzilla importer

In JIRA 4.0-standalone we had a copy of log4j in atlassian-jira/WEB-INF/lib. This no longer exists in JIRA 4.1. This means that our instructions at http://confluence.atlassian.com/display/JIRA/Modifying+the+Bugzilla+Importer no longer work: ant can't compile the file because there is no copy of log4j on the classpath.

As a workaround the user can explicitly put a copy of log4j in external-source/lib and then running ant.