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](#112268 (comment)).

Related tracking issue for build configuration: #103595

.github/workflows/ci.yml

@@ -337,7 +337,7 @@ jobs:
           - name: dist-x86_64-apple
             env:
               SCRIPT: "./x.py dist bootstrap --include-default-paths --host=x86_64-apple-darwin --target=x86_64-apple-darwin"
-              RUST_CONFIGURE_ARGS: "--enable-full-tools --enable-sanitizers --enable-profiler --set rust.jemalloc --set rust.lto=thin"
+              RUST_CONFIGURE_ARGS: "--enable-full-tools --enable-sanitizers --enable-profiler --set rust.jemalloc --set rust.lto=thin --set rust.codegen-units=1"
               RUSTC_RETRY_LINKER_ON_SEGFAULT: 1
               MACOSX_DEPLOYMENT_TARGET: 10.12
               SELECT_XCODE: /Applications/Xcode_14.3.1.app

src/ci/github-actions/ci.yml

@@ -540,7 +540,7 @@ jobs:
           - name: dist-x86_64-apple
             env:
               SCRIPT: ./x.py dist bootstrap --include-default-paths --host=x86_64-apple-darwin --target=x86_64-apple-darwin
-              RUST_CONFIGURE_ARGS: --enable-full-tools --enable-sanitizers --enable-profiler --set rust.jemalloc --set rust.lto=thin
+              RUST_CONFIGURE_ARGS: --enable-full-tools --enable-sanitizers --enable-profiler --set rust.jemalloc --set rust.lto=thin --set rust.codegen-units=1
               RUSTC_RETRY_LINKER_ON_SEGFAULT: 1
               MACOSX_DEPLOYMENT_TARGET: 10.12
               SELECT_XCODE: /Applications/Xcode_14.3.1.app