Merge ref 'd087f112b7d1:/library/compiler-builtins' from https://github.com/rust-lang/rust

Pull recent changes from rust-lang/rust via Josh.

Upstream ref: d087f11
Filtered ref: 2d43ce8ac022170e5383f7e5a188b55564b6566a

Author: tgross35

.github/workflows/ci.yml

@@ -11,6 +11,10 @@ name: CI
 on:
   push:
     branches:
+      # CI on master only serves for caching citool builds for the `calculate_matrix` job.
+      # In order to use GHA cache on PR CI (and auto/try) jobs, we need to write to it
+      # from the default branch.
+      - master
       - auto
       - try
       - try-perf
@@ -60,12 +64,18 @@ jobs:
         uses: Swatinem/rust-cache@9d47c6ad4b02e050fd481d890b2ea34778fd09d6 # v2.7.8
         with:
           workspaces: src/ci/citool
+      - name: Test citool
+        # Only test citool on the auto branch, to reduce latency of the calculate matrix job
+        # on PR/try builds.
+        if: ${{ github.ref == 'refs/heads/auto' }}
+        run: |
+          cd src/ci/citool
+          CARGO_INCREMENTAL=0 cargo test
       - name: Calculate the CI job matrix
         env:
           COMMIT_MESSAGE: ${{ github.event.head_commit.message }}
         run: |
           cd src/ci/citool
-          CARGO_INCREMENTAL=0 cargo test
           CARGO_INCREMENTAL=0 cargo run calculate-job-matrix >> $GITHUB_OUTPUT
         id: jobs
   job: