[llvm] [libcxx] Add libc++ github actions workflow to replace buildkite (PR #71836)

[Louis Dionne via llvm-commits]

================
@@ -0,0 +1,112 @@
+name: Build and Test libc++
+
+on: pull_request
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number }}
+  cancel-in-progress: true
+
+
+env:
+  CMAKE: "/opt/bin/cmake"
+
+# Comment
+jobs:
+  stage1:
+    runs-on: libcxx-runners-16
+    continue-on-error: false
+    strategy:
+      fail-fast: true
+      matrix:
+        config: [ 'generic-cxx26', 'generic-cxx03', 'generic-modules' ]
+        cc: [ 'clang-18' ]
+        cxx: [ 'clang++-18' ]
+        include:
+          - config: 'generic-gcc'
+            cc: 'gcc-13'
+            cxx: 'g++-13'
+    steps:
+      - uses: actions/checkout at 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 at v3
+        if: always()
+        with:
+          name: ${{ matrix.config }}-${{ matrix.cxx }}-results
+          path: |
+            "**/test-results.xml"
+            "**/*.abilist"
+  stage2:
+    runs-on: libcxx-runners-8
+    needs: [ stage1  ]
+    continue-on-error: false
+    strategy:
+      fail-fast: true
+      matrix:
+        config: [ 'generic-cxx11', 'generic-cxx14', 'generic-cxx17',
+                  'generic-cxx20', 'generic-cxx23' ]
+        include:
+          - config: 'generic-gcc-cxx11'
+            cc: 'gcc-13'
+            cxx: 'g++-13'
+          - config: 'generic-cxx23'
+            cc: 'clang-16'
+            cxx: 'clang++-16'
+          - config: 'generic-cxx23'
+            cc: 'clang-17'
+            cxx: 'clang++-17'
+    steps:
+      - uses: actions/checkout at v4
+      - name: ${{ matrix.config }}
+        run: libcxx/utils/ci/run-buildbot ${{ matrix.config }}
+        env:
+          CC: 'clang-18'
+          CXX: 'clang++-18'
+      - uses: actions/upload-artifact at v3
+        if: always()
+        with:
+          name: ${{ matrix.config }}-results
+          path: |
+            **/test-results.xml
+            **/*.abilist
+  stage3:
+    needs: [ stage1, stage2 ]
+    continue-on-error: false
+    strategy:
+      fail-fast: true
+      max-parallel: 8
+      matrix:
+        config: [ 'generic-no-threads', 'generic-no-filesystem', 'generic-no-random_device',
+          'generic-no-localization', 'generic-no-unicode', 'generic-no-wide-characters',
+          'generic-no-experimental', 'generic-no-exceptions', 'generic-abi-unstable',  'generic-hardening-mode-fast',
+          'generic-hardening-mode-fast-with-abi-breaks', 'generic-hardening-mode-extensive',
+          'generic-hardening-mode-debug', 'generic-with_llvm_unwinder', 'generic-static', 'generic-merged',
+          'generic-modules-lsv', 'generic-no-tzdb' ]
+        machine: [ 'libcxx-runners-8' ]
+        include:
+        - config: 'generic-asan'
+          machine: libcxx-runners-16
+        - config: 'generic-tsan'
+          machine: libcxx-runners-16
+        - config: 'generic-ubsan'
+          machine: libcxx-runners-8
+        - config: 'generic-msan'
+          machine: libcxx-runners-30
+    runs-on: ${{ matrix.machine }}
+    steps:
+      - uses: actions/checkout at v4
+      - name: ${{ matrix.config }}
+        run: libcxx/utils/ci/run-buildbot ${{ matrix.config }}
+        env:
+          CC: clang-18
+          CXX: clang++-18
----------------
ldionne wrote:

```suggestion
          CC: clang-${{ LLVM_HEAD_VERSION }}
          CXX: clang++-${{ LLVM_HEAD_VERSION }}
```

https://github.com/llvm/llvm-project/pull/71836