I figured out a way that seems to work well.
First, setup the maven-dependency-plugin to always run the "properties" goal.
<plugin>
<artifactId>maven-dependency-plugin</artifactId>
<version>2.5.1</version>
<executions>
<execution>
<id>getClasspathFilenames</id>
<goals>
<goal>properties</goal>
</goals>
</execution>
</executions>
</plugin>
Later on, use the property it sets as documented here with the form:
groupId:artifactId:type:[classifier]
e.g.
<argument>-javaagent:${mygroup:eclipselink:jar}</argument>