Generate aggregate Javadoc without duplicate execution of phase compile.

• The standard goals aggregate and test-aggregate invoke separate lifecyles compile and test-compile.
• In a CI environment you now might execute something like mvn clean deploy site site-deploy.
• During site build the standard reports will trigger compile or test-compile again, depending on your build this may take some time, because stuff like enforcer or generating stubs from a WDSL will be invoked again, which may lead to longer build times.
• As of version 3.0.1 two new reports are defined, aggregate-no-fork and test-aggregate-no-fork which will not trigger above phases a second time.
• Configure this in your reporting section as follows:

  <project>
    ...
    <reporting>
      <excludeDefaults>true</excludeDefaults>
      <plugins>
        <plugin>
          <groupId>org.apache.maven.plugins</groupId>
          <artifactId>maven-javadoc-plugin</artifactId>
          <version>3.1.0</version>
          <reportSets>
            <reportSet>
              <reports>
                <report>aggregate-no-fork</report>
                <report>test-aggregate-no-fork</report>
              </reports>
            </reportSet>
          </reportSets>
        </plugin>
      </plugins>
    </reporting>
    ...
  </project>