CI: Enable testing on macOS

Author: amotl

.github/workflows/main.yml

@@ -20,7 +20,7 @@ jobs:
     strategy:
       matrix:
         crate-version: [nightly]
-        os: [ubuntu-latest]
+        os: [ubuntu-latest, macos-latest]
         sqla-version: ['1.1.18', '1.2.19', '1.3.20']
         python-version: [3.5, 3.6, 3.7, 3.8, 3.9]
 
@@ -53,4 +53,9 @@ jobs:
       - name: Test
         run: |
           bin/flake8
-          bin/coverage run bin/test -vv1
+
+          test_program=bin/test
+          if [ ${{ matrix.os }} = "macos-latest" ]; then
+            test_program=bin/test-quick
+          fi
+          bin/coverage run $test_program -vv1