[libc++] Move some macOS CI jobs to Github actions

This is an attempt to decouple macOS CI testing from BuildKite, which
would make the maintenance of macOS CI easier and more accessible to
all contributors. Right now, the macOS CI is running entirely on machines
owned by the LLVM Foundation with only a small set of contributors having
direct access to them.

The story for performing back-deployment testing still needs to be
figured out, so for now we are retaining some jobs under BuildKite.

.github/workflows/libcxx-build-and-test.yaml

@@ -85,6 +85,7 @@ jobs:
             **/CMakeError.log
             **/CMakeOutput.log
             **/crash_diagnostics/*
+
   stage2:
     if: github.repository_owner == 'llvm'
     runs-on: libcxx-runners-8-set
@@ -134,6 +135,7 @@ jobs:
             **/CMakeError.log
             **/CMakeOutput.log
             **/crash_diagnostics/*
+
   stage3:
     if: github.repository_owner == 'llvm'
     needs: [ stage1, stage2 ]
@@ -199,6 +201,38 @@ jobs:
             **/CMakeError.log
             **/CMakeOutput.log
             **/crash_diagnostics/*
+
+  macos:
+    runs-on: macos-latest
+    needs: [ stage1 ]
+    strategy:
+      fail-fast: false
+      matrix:
+        config: [
+          generic-cxx03,
+          generic-cxx23,
+          generic-modules,
+          apple-system
+        ]
+    steps:
+      - uses: actions/checkout@v4
+      - uses: maxim-lobanov/setup-xcode@v1
+        with:
+          xcode-version: 'latest-stable'
+      - name: Build and test
+        run: |
+          bash libcxx/utils/ci/run-buildbot ${{ matrix.config }}
+      - uses: actions/upload-artifact@26f96dfa697d77e81fd5907df203aa23a56210a8 # v4.3.0
+        if: always()  # Upload artifacts even if the build or test suite fails
+        with:
+          name: macos-${{ matrix.config }}-results
+          path: |
+            **/test-results.xml
+            **/*.abilist
+            **/CMakeError.log
+            **/CMakeOutput.log
+            **/crash_diagnostics/*
+
   windows:
     runs-on: windows-2022
     needs: [ stage1 ]

libcxx/utils/ci/buildkite-pipeline.yml

@@ -56,47 +56,8 @@ environment_definitions:
 
 
 steps:
-- group: ':mac: Apple'
+- group: ':mac: Apple Backdeployment'
   steps:
-  - label: MacOS x86_64
-    command: libcxx/utils/ci/run-buildbot generic-cxx23
-    agents:
-      queue: libcxx-builders
-      os: macos
-      arch: x86_64
-    <<: *common
-
-  - label: MacOS arm64
-    command: libcxx/utils/ci/run-buildbot generic-cxx23
-    agents:
-      queue: libcxx-builders
-      os: macos
-      arch: arm64
-    <<: *common
-
-  - label: MacOS with Modules
-    command: libcxx/utils/ci/run-buildbot generic-modules
-    agents:
-      queue: libcxx-builders
-      os: macos
-    <<: *common
-
-  - label: MacOS with C++03
-    command: libcxx/utils/ci/run-buildbot generic-cxx03
-    agents:
-      queue: libcxx-builders
-      os: macos
-    <<: *common
-
-    # Build with the configuration we use to generate libc++.dylib on Apple platforms
-  - label: Apple system
-    command: libcxx/utils/ci/run-buildbot apple-system
-    agents:
-      queue: libcxx-builders
-      os: macos
-      arch: arm64 # This can technically run on any architecture, but we have more resources on arm64 so we pin this job to arm64
-    <<: *common
-
   - label: Apple back-deployment macosx10.13
     command: libcxx/utils/ci/run-buildbot apple-system-backdeployment-10.13
     agents:
@@ -121,6 +82,23 @@ steps:
       arch: x86_64 # TODO: Remove this once we are able to run back-deployment on arm64 again, since this isn't x86_64 specific
     <<: *common
 
+    # TODO: Re-enable this once we've figured out how to run back-deployment testing on arm64 on recent OSes
+    # - label: "Apple back-deployment macosx11.0 arm64"
+    #   command: "libcxx/utils/ci/run-buildbot apple-system-backdeployment-11.0"
+    #   artifact_paths:
+    #     - "**/test-results.xml"
+    #     - "**/*.abilist"
+    #   agents:
+    #     queue: "libcxx-builders"
+    #     os: "macos"
+    #     arch: "arm64"
+    #   retry:
+    #     automatic:
+    #       - exit_status: -1  # Agent was lost
+    #         limit: 2
+    #   timeout_in_minutes: 120
+
+
 - group: ARM
   steps:
   - label: AArch64
@@ -230,20 +208,3 @@ steps:
       queue: libcxx-builders
       os: android
     <<: *common
-
-
-    # TODO: Re-enable this once we've figured out how to run back-deployment testing on arm64 on recent OSes
-    # - label: "Apple back-deployment macosx11.0 arm64"
-    #   command: "libcxx/utils/ci/run-buildbot apple-system-backdeployment-11.0"
-    #   artifact_paths:
-    #     - "**/test-results.xml"
-    #     - "**/*.abilist"
-    #   agents:
-    #     queue: "libcxx-builders"
-    #     os: "macos"
-    #     arch: "arm64"
-    #   retry:
-    #     automatic:
-    #       - exit_status: -1  # Agent was lost
-    #         limit: 2
-    #   timeout_in_minutes: 120