With this PR I am trying to address the issue I reported at https://issues.apache.org/jira/browse/MJAVADOC-811

In corporate environments system admins may have configured a default directory for newly spawned cmd.exe processes which results in javadoc being executed in the wrong folder/wrong drive. By specifying the /D flag the cmd.exe will always execute the given command in the current working directory as expected.

The surprising AutoRun behavior is explained in Microsoft's devblog: Hidden gotcha: The command processor's AutoRun setting