Attach source for tycho build

gistfile1.xml

<plugin>
<!-- TODO remove workaround when
             https://issues.sonatype.org/browse/TYCHO-473
             is fixed -->
<groupId>org.sonatype.tycho</groupId>
<artifactId>maven-osgi-source-plugin</artifactId>
<version>${tycho.version}</version>
<executions>
<execution>
<id>attach-source</id>
<phase>process-classes</phase>
<goals>
<goal>plugin-source</goal>
</goals>
</execution>
</executions>
</plugin>