JBDS doesn't ship with Mylyn/Bugzilla. It is not required for build or installation.
However, the Mylyn/Bugzilla integration should be available on discovery site, so this dependency was moved to jbtcentral target: https://github.com/mickaelistria/jbosstools-discovery/commit/0045138841aae5d23e4f97f3b2cb1010d466c580