Add in the root pom of joram a pluginManagement section that use the property maven-assembly-plugin.version declared in the same pom to define the version of assembly plugin to use.
Use version 3.3.0 (i.e. latest one available at the time of commit) by default.
Override the version to 2.6 for jmscheck module as it is the latest one to include the goal 'attached' that is used by jmscheck.