To set "supergrammars" available to some grammar, use the <grammarDefs> configuration in your pom:
<project>
...
<build>
<plugins>
...
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>antlr-maven-plugin</artifactId>
<version>2.2</version>
<configuration>
<!--
By default, grammar files are in ${basedir}/src/main/antlr
-->
<grammarDefs>
<grammar>
<name>StdCParser.g</name>
</grammar>
<grammar>
<name>GnuCParser.g</name>
<glib>StdCParser.g</glib>
</grammar>
<grammar>
<name>GnuCTreeParser.g</name>
</grammar>
<grammar>
<name>GnuCEmitter.g</name>
<glib>GnuCTreeParser.g</glib>
</grammar>
</grammarDefs>
</configuration>
</plugin>
...
</plugins>
</build>
...
</project>