The setup.py script assumes it is being run from the top-level project
directory with all filenames relative to that location. This may not
always be the case.

Attached is a patch that ensure the working directory is changed so that
the relative filename locations will work no mater where the setup.py
script is invoked from.

I have avoid commit this patch directly in case others believe it is too
hackish and the relative filenames should actually be fixed.