Merge commit '1600cf040584' from llvm.org/release/21.x into stable/21.x

Author: git apple-llvm automerger

.github/workflows/premerge.yaml

@@ -149,7 +149,7 @@ jobs:
         uses: llvm/actions/install-ninja@main
       - name: Build and Test
         run: |
-          source <(git diff --name-only HEAD~2..HEAD | python3 .ci/compute_projects.py)
+          source <(git diff --name-only HEAD~1...HEAD | python3 .ci/compute_projects.py)
 
           if [[ "${projects_to_build}" == "" ]]; then
             echo "No projects to build"