Auto merge of #103647 - lqd:osx-x64-lto, r=Mark-Simulacrum

Enable ThinLTO for rustc on `x86_64-apple-darwin`

Local measurements seemed to show an improvement on a couple benchmarks, so I'd like to test real CI builds, and see if the builder doesn't timeout with the expected slight increase in build times.

Let's start with x64 rustc ThinLTO, and then figure out the file structure to configure LLVM ThinLTO. Maybe we'll then try `aarch64` builds since that also looked good locally.

.github/workflows/ci.yml

@@ -301,7 +301,7 @@ 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 llvm.ninja=false"
+              RUST_CONFIGURE_ARGS: "--enable-full-tools --enable-sanitizers --enable-profiler --set rust.jemalloc --set llvm.ninja=false --set rust.lto=thin"
               RUSTC_RETRY_LINKER_ON_SEGFAULT: 1
               MACOSX_DEPLOYMENT_TARGET: 10.7
               SELECT_XCODE: /Applications/Xcode_13.4.1.app

src/ci/github-actions/ci.yml

@@ -467,7 +467,7 @@ 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 llvm.ninja=false
+              RUST_CONFIGURE_ARGS: --enable-full-tools --enable-sanitizers --enable-profiler --set rust.jemalloc --set llvm.ninja=false --set rust.lto=thin
               RUSTC_RETRY_LINKER_ON_SEGFAULT: 1
               MACOSX_DEPLOYMENT_TARGET: 10.7
               SELECT_XCODE: /Applications/Xcode_13.4.1.app