Thank you @akafred for this workaround:
<plugin>
<groupId>de.shadowhunt.maven.plugins</groupId>
<artifactId>package-info-maven-plugin</artifactId>
<version>2.0.0</version>
</plugin>
<plugin>
<!-- We generate package-info.java-files to get information from Jdepend in Sonar -->
<groupId>de.shadowhunt.maven.plugins</groupId>
<artifactId>package-info-maven-plugin</artifactId>
<configuration>
<packages>
<package>
</package>
</packages>
<!-- Sonar doesn't like the files to be in generated-sources :-(
so we have to put them in src-folder - however we don't check them in -->
<outputDirectory>${project.basedir}/src/main/java</outputDirectory>
</configuration>
<executions>
<execution>
<phase>generate-sources</phase>
<goals>
<goal>package-info</goal>
</goals>
</execution>
</executions>
</plugin>