gmaven-plugin does not support <source> and <target> configuration options

The gmaven-plugin does not support using source and target options which the maven-compiler-plugin supports:
<configuration>
<source>1.5</source>
<target>1.5</target>
</configuration>

This makes it hard to compile java code with 1.5+ features, such as annotations. The only workaround I found was to pass in the variables on the command line:
mvn clean test -Dmaven.compiler.source=1.5 -Dmaven.compiler.target=1.5