I forgot to mention another change ...

Danny Milosavljevic <dannym@scratchpost.org> writes:
> +               ;; Crate::load_extern_crate ignores the search path, so make
> +               ;; the situation easier for it.
> +               (copy-recursively (string-append rustc-bootstrap "/lib/mrust")
> +                                 "output")

This hunk is exactly identical to the next expression some lines below,
I removed it from the original patch to avoid a build failure.