Auto merge of #112268 - lqd:osx-1cgu, r=Kobzol

Build `rustc` with 1CGU on `x86_64-apple-darwin`

Distribute `x86_64-apple-darwin` artifacts built with `rust.codegen-units=1`, like we already do on Linux.

1) effect on code size on `x86_64-apple-darwin`: it's a 11.14% reduction on `librustc_driver.dylib`
- before, [`41d97c8a5dea2731b0e56fe97cd7cb79e21cff79`](https://ci-artifacts.rust-lang.org/rustc-builds/41d97c8a5dea2731b0e56fe97cd7cb79e21cff79/rustc-nightly-x86_64-apple-darwin.tar.xz): 161232048
- after, [`7549dbdc09f0c4f6cc84002ac03081828054784b`](https://ci-artifacts.rust-lang.org/rustc-builds/7549dbdc09f0c4f6cc84002ac03081828054784b/rustc-nightly-x86_64-apple-darwin.tar.xz): 143256928

2) time it took on CI:
- the [first `try` build](https://github.com/rust-lang-ci/rust/actions/runs/8155512915/job/22291187124) took: 1h 33m
- the [second `try` build](https://github.com/rust-lang-ci/rust/actions/runs/8157057880/job/22295839911) took: 1h 45m

3) most recent perf results on (a noisy) x64 mac are [here](rust-lang/rust#112268 (comment)).

Related tracking issue for build configuration: #103595

Author: bors