Cython build GH action: support native (arm64 on M1/M2) and Intel (x8…

…6_64) builds on macOS

.github/workflows/build_cython.yml

@@ -21,6 +21,11 @@ jobs:
       matrix:
         os: [ubuntu-latest, windows-latest, macos-latest]
         python-version: ['3.11']
+        include:
+          - os: macos-latest
+            target: native
+          - os: macos-latest
+            target: intel
 
     steps:
     - uses: actions/checkout@v3
@@ -36,7 +41,17 @@ jobs:
         python -m pip install cython numpy setuptools wheel
 
     - name: Build Cython extensions
-      run: python cy_setup.py build_ext --inplace
+      env:
+        ARCHFLAGS: ${{ matrix.target == 'intel' && '-arch x86_64' || '' }}
+      run: |
+        if [ "${{ matrix.os }}" == "macos-latest" ] && [ "${{ matrix.target }}" == "intel" ]; then
+          PYTHON_CROSSENV=$(pwd)/crossenv
+          python -m pip install crossenv
+          python -m crossenv $(which python3) $PYTHON_CROSSENV
+          source $PYTHON_CROSSENV/bin/activate
+          python -m pip install cython numpy setuptools wheel
+        fi
+        python cy_setup.py build_ext --inplace
 
     - name: Rename compiled extensions
       shell: bash
@@ -45,11 +60,16 @@ jobs:
         if [ "${{ matrix.os }}" == "windows-latest" ]; then
           echo "Windows build - keeping original name"
         elif [ "${{ matrix.os }}" == "macos-latest" ]; then
+          if [ "${{ matrix.target }}" == "intel" ]; then
+            arch="x86_64"
+          else
+            arch=$(uname -m)
+          fi
           # First remove target if it exists
-          rm -f rfmesh_visibility.cpython-311-darwin-$(uname -m).so
+          rm -f rfmesh_visibility.cpython-311-darwin-${arch}.so
           # Then move the file
           for f in rfmesh_visibility*.so; do
-            mv "$f" rfmesh_visibility.cpython-311-darwin-$(uname -m).so
+            mv "$f" rfmesh_visibility.cpython-311-darwin-${arch}.so
           done
         elif [ "${{ matrix.os }}" == "ubuntu-latest" ]; then
           # First remove target if it exists