[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

@@ -47,188 +47,36 @@ env:
 
 
 jobs:
-  stage1:
-    if: github.repository_owner == 'llvm'
-    runs-on: libcxx-runners-8-set
-    continue-on-error: false
+  macos:
+    runs-on: macos-14
     strategy:
       fail-fast: false
       matrix:
         config: [
-          'generic-cxx03',
-          'generic-cxx26',
-          'generic-modules'
+          generic-cxx03,
+          generic-cxx23,
+          generic-modules,
+          apple-system
         ]
-        cc: [  'clang-19' ]
-        cxx: [ 'clang++-19' ]
-        include:
-          - config: 'generic-gcc'
-            cc: 'gcc-14'
-            cxx: 'g++-14'
     steps:
       - uses: actions/checkout@v4
-      - name: ${{ matrix.config }}.${{ matrix.cxx }}
-        run: libcxx/utils/ci/run-buildbot ${{ matrix.config }}
-        env:
-          CC: ${{ matrix.cc }}
-          CXX: ${{ matrix.cxx }}
-      - uses: actions/upload-artifact@26f96dfa697d77e81fd5907df203aa23a56210a8 # v4.3.0
-        if: always()
+      - uses: maxim-lobanov/setup-xcode@v1
         with:
-          name: ${{ matrix.config }}-${{ matrix.cxx }}-results
-          path: |
-            **/test-results.xml
-            **/*.abilist
-            **/CMakeError.log
-            **/CMakeOutput.log
-            **/crash_diagnostics/*
-  stage2:
-    if: github.repository_owner == 'llvm'
-    runs-on: libcxx-runners-8-set
-    needs: [ stage1 ]
-    continue-on-error: false
-    strategy:
-      fail-fast: false
-      matrix:
-        config: [
-          'generic-cxx11',
-          'generic-cxx14',
-          'generic-cxx17',
-          'generic-cxx20',
-          'generic-cxx23'
-        ]
-        cc: [ 'clang-19' ]
-        cxx: [ 'clang++-19' ]
-        include:
-          - config: 'generic-gcc-cxx11'
-            cc: 'gcc-14'
-            cxx: 'g++-14'
-          - config: 'generic-cxx23'
-            cc: 'clang-17'
-            cxx: 'clang++-17'
-          - config: 'generic-cxx26'
-            cc: 'clang-18'
-            cxx: 'clang++-18'
-    steps:
-      - uses: actions/checkout@v4
-      - name: ${{ matrix.config }}
-        run: libcxx/utils/ci/run-buildbot ${{ matrix.config }}
-        env:
-          CC: ${{ matrix.cc }}
-          CXX: ${{ matrix.cxx }}
+          xcode-version: 'latest-stable'
+      - uses: seanmiddleditch/gha-setup-ninja@master
+      - name: Build and test
+        run: |
+          python3 -m venv .venv
+          source .venv/bin/activate
+          python3 -m pip install psutil
+          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: ${{ matrix.config }}-${{ matrix.cxx }}-results
-          path: |
-            **/test-results.xml
-            **/*.abilist
-            **/CMakeError.log
-            **/CMakeOutput.log
-            **/crash_diagnostics/*
-  stage3:
-    if: github.repository_owner == 'llvm'
-    needs: [ stage1, stage2 ]
-    continue-on-error: false
-    strategy:
-      fail-fast: false
-      max-parallel: 8
-      matrix:
-        config: [
-          'generic-abi-unstable',
-          'generic-hardening-mode-debug',
-          'generic-hardening-mode-extensive',
-          'generic-hardening-mode-fast',
-          'generic-hardening-mode-fast-with-abi-breaks',
-          'generic-merged',
-          'generic-modules-lsv',
-          'generic-no-exceptions',
-          'generic-no-experimental',
-          'generic-no-filesystem',
-          'generic-no-localization',
-          'generic-no-random_device',
-          'generic-no-threads',
-          'generic-no-tzdb',
-          'generic-no-unicode',
-          'generic-no-wide-characters',
-          'generic-no-rtti',
-          'generic-optimized-speed',
-          'generic-static',
-          # TODO Find a better place for the benchmark and bootstrapping builds to live. They're either very expensive
-          # or don't provide much value since the benchmark run results are too noise on the bots.
-          'benchmarks',
-          'bootstrapping-build'
-        ]
-        machine: [ 'libcxx-runners-8-set' ]
-        include:
-        - config: 'generic-cxx26'
-          machine: libcxx-runners-8-set
-        - config: 'generic-asan'
-          machine: libcxx-runners-8-set
-        - config: 'generic-tsan'
-          machine: libcxx-runners-8-set
-        - config: 'generic-ubsan'
-          machine: libcxx-runners-8-set
-        # Use a larger machine for MSAN to avoid timeout and memory allocation issues.
-        - config: 'generic-msan'
-          machine: libcxx-runners-8-set
-    runs-on: ${{ matrix.machine }}
-    steps:
-      - uses: actions/checkout@v4
-      - name: ${{ matrix.config }}
-        run: libcxx/utils/ci/run-buildbot ${{ matrix.config }}
-        env:
-          CC: clang-19
-          CXX: clang++-19
-      - uses: actions/upload-artifact@26f96dfa697d77e81fd5907df203aa23a56210a8 # v4.3.0
-        if: always()
-        with:
-          name: ${{ matrix.config }}-results
+          name: macos-${{ matrix.config }}-results
           path: |
             **/test-results.xml
             **/*.abilist
             **/CMakeError.log
             **/CMakeOutput.log
             **/crash_diagnostics/*
-  windows:
-    runs-on: windows-2022
-    needs: [ stage1 ]
-    strategy:
-      fail-fast: false
-      matrix:
-        include:
-        - { config: clang-cl-dll, mingw: false }
-        - { config: clang-cl-static, mingw: false }
-        - { config: clang-cl-no-vcruntime, mingw: false }
-        - { config: clang-cl-debug, mingw: false }
-        - { config: clang-cl-static-crt, mingw: false }
-        - { config: mingw-dll, mingw: true }
-        - { config: mingw-static, mingw: true }
-        - { config: mingw-dll-i686, mingw: true }
-    steps:
-      - uses: actions/checkout@v4
-      - name: Install dependencies
-        run: |
-          choco install -y ninja
-          pip install psutil
-      - name: Install a current LLVM
-        if: ${{ matrix.mingw != true }}
-        run: |
-          choco install -y llvm --version=18.1.6 --allow-downgrade
-      - name: Install llvm-mingw
-        if: ${{ matrix.mingw == true }}
-        run: |
-          curl -LO https://github.com/mstorsjo/llvm-mingw/releases/download/20240606/llvm-mingw-20240606-ucrt-x86_64.zip
-          powershell Expand-Archive llvm-mingw*.zip -DestinationPath .
-          del llvm-mingw*.zip
-          mv llvm-mingw* c:\llvm-mingw
-          echo "c:\llvm-mingw\bin" | Out-File -FilePath $Env:GITHUB_PATH -Encoding utf8 -Append
-      - name: Add Git Bash to the path
-        run: |
-          echo "c:\Program Files\Git\usr\bin" | Out-File -FilePath $Env:GITHUB_PATH -Encoding utf8 -Append
-      - name: Set up the MSVC dev environment
-        if: ${{ matrix.mingw != true }}
-        uses: ilammy/msvc-dev-cmd@v1
-      - name: Build and test
-        run: |
-          bash libcxx/utils/ci/run-buildbot ${{ matrix.config }}