Make additional-config-file paths relative to the Hipcheck.kdl file, not to the path the user is in.

[alilleybrinker]

Right now those config paths basically lock the user into running things from a single location, but instead those paths should be relative to the file, not the user.

[j-lanson]

Because the additional-config paths are arguments to plugins, we don't make any assumptions about their contents before sending them to the plugin during the config step. The plugin has no idea where the Hipcheck.kdl file was located, so it doesn't have the necessary info to resolve any path-representing strings it receives as relative to Hipcheck.kdl.