Do not remove `super` keyword from `super let`

This is affecting a macro in the standard library:

https://github.com/rust-lang/rust/blob/bc7512ee6309ee7e8cacf87b94aa6d1f550c9d99/library/core/src/pin.rs#L1945

I added an exception in 6f6a9a5, but I'd like to remove it eventually, so opening this in-tree to not block this on the next rustfmt sync.

r? `@calebcartwright` or `@ytmimi`

…errors

Stage0 bootstrap update

This PR [follows the release process](https://forge.rust-lang.org/release/process.html#master-bootstrap-update-tuesday) to update the stage0 compiler.

The only thing of note is 58651d1, which was flagged by clippy as a correctness fix. I think allowing that lint in our case makes sense, but it's worth to have a second pair of eyes on it.

r? `@Mark-Simulacrum`

Update `ctrlc`, `libloading` and `nix` for rustc

The main purpose is to update `nix` to 0.30.1. It adds support for cygwin.