We don't change anything about compilation-setup, we just immediately jump to
Rust, making the eventual final swap to a Rust entrypoint very easy.
There are some string-usage and format-string differences that are generally
quite messy.
Just another version of the error. We still want to get a bug if it
ever triggers a *wrong* error, so we still list all the options
instead of going for `.*option:.*Z.*`.
Fixes#6554