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.

diff --cc .github/workflows/ci.yml
index b29b3a418038ee4407809a38b67f67b7dcf3a010,e39f71cdb82c93006cd3f1d01c96f7e280e3e27d..2b6e96b467e3555d0611aa845aabd522b575714c
--- 1/.github/workflows/ci.yml
--- 2/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@@ -301,10 -298,9 +301,10 @@@ 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
                NO_LLVM_ASSERTIONS: 1
                NO_DEBUG_ASSERTIONS: 1
                NO_OVERFLOW_CHECKS: 1

diff --cc src/ci/github-actions/ci.yml
index 5a0397a3d123cf714bb63dbf40b4a87a9ae9f69a,ecc6887dad8d44b3beb716666f5f2cff6cb592c4..d1ba46ad30de6d08c82176a41b7e894c87358704
--- 1/src/ci/github-actions/ci.yml
--- 2/src/ci/github-actions/ci.yml
+++ b/src/ci/github-actions/ci.yml
@@@ -467,10 -463,9 +467,10 @@@ 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
                NO_LLVM_ASSERTIONS: 1
                NO_DEBUG_ASSERTIONS: 1
                NO_OVERFLOW_CHECKS: 1