Dedicated setup.py test workflow

Verifies the `setup.py` creates the archive properly by installing
it locally and running basic toolchain commands.

.github/workflows/setup.yml

@@ -0,0 +1,35 @@
+name: setup
+
+on: [push, pull_request]
+
+jobs:
+  checks:
+    runs-on: macos-latest
+    steps:
+    - name: Checkout kivy-ios
+      uses: actions/checkout@v2
+    - name: Set up Python 3.7
+      uses: actions/setup-python@v1.1.0
+      with:
+        python-version: 3.7
+    - name: Install dependencies
+      run: |
+        pip install --upgrade setuptools wheel twine
+    - name: sdist bdist_wheel
+      run: |
+        python setup.py sdist bdist_wheel
+    - name: Twine check
+      run: |
+        twine check dist/*
+    - name: Local install
+      run: |
+        python -m venv venv
+        . venv/bin/activate
+        pip install dist/kivy-ios-*.tar.gz
+        pip install Cython==0.29.17
+        brew install autoconf automake libtool pkg-config
+    - name: Basic toolchain commands
+      run: |
+        . venv/bin/activate
+        toolchain --help
+        toolchain recipes