Maven Package making MAVEN_OPTS difficult to set

Setting -Xmx in ENV MAVEN_OPTS on the dockerfile doesn’t seem to work because the /etc/mavenrc is setting it and putting the Xmx to the end of the arguments.
Wouldn’t be better to let the JVM set the default Heap Size or let the user set MAVEN_OPTS easily in the Dockerfile with ENV?

(from redmine: issue id 8762, created on 2018-04-03)