Add support for GitHub Actions

Closes pypa#159

.github/workflows/test.yml

@@ -0,0 +1,28 @@
+name: Test
+
+on: [push, pull_request]
+
+jobs:
+  test:
+    name: Test cibuildwheel on ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ubuntu-18.04, windows-latest, macos-latest]
+    steps:
+    - uses: actions/checkout@v1
+    - uses: actions/setup-python@v1
+      name: Install Python ${{ matrix.python_version }}
+      with:
+        python-version: "3.7"
+
+    - name: Install dependencies
+      run: |
+        python -m pip install -r requirements-dev.txt
+    - name: Install Visual C++ for Python 2.7
+      if: startsWith(matrix.os, 'windows')
+      run: |
+        choco install vcpython27 -f -y
+    - name: Test cibuildwheel
+      run: |
+        python ./bin/run_tests.py

cibuildwheel/__main__.py

@@ -83,6 +83,13 @@ def main():
                 platform = 'macos'
             elif os.environ['AGENT_OS'] == 'Windows_NT':
                 platform = 'windows'
+        elif 'GITHUB_WORKFLOW' in os.environ:
+            if sys.platform.startswith('linux'):
+                platform = 'linux'
+            elif sys.platform.startswith('darwin'):
+                platform = 'macos'
+            else:
+                platform = 'windows'
 
         if platform is None:
             print('cibuildwheel: Unable to detect platform. cibuildwheel should run on your CI server, '