Working on a v6 for this, Efraim pointed out to me that a lot

of the intermediate packages arent building as-is after

removing all the `skip-build? #t`. v6 will address that, and

should be done in the next day or so.

So far the only package particularly egregious to get a

decent method of building + testing is `rust-diffus` + its

derive macro crate (upstream is <https://github.com/distil/diffus/tree/master>).

Any help/advice on that one would be great as:

- they both reference a README that is in a parent directory

  - easy enough and is worked around to build the

    `diffus` crate proper.

- the derive macro is in a workspace, and no incantation

  of `--exclude`  / `--manifest-path` etc will only build the

  `-derive` without the `diffus` proper.

For now I just have the `rust-diffus-derive` package

marked as `#:skip-build? #t`.

- Jordan