Respect the XDG Base Directory Specification

Running the `pack download` command in codeql writes results to a $HOME/.codeql directory.

It would be nice if codeql conformed to the freedesktop guidelines about where to write user data, as specified here: https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html

That would make it easier to know where the programs data is located, and not clutter my home directory.