Was going to add this comment, but the code was wrong when doxyqml was invoked with relative paths anyway.

        # Pick parent of `dir`, but abort if we reached the root. Checking
        # for the root is slightly tricky: On POSIX platforms forms we have
        # `dirname("/home")` and `dirname("/")` both returning "/". In
        # opposition to that `dirname("C:/Users")` on Windows returns just
        # "C:". This is pretty bad, since "C:" is not an absolute path and
        # therefore `dirname("C:")` returns just an empty string ("").