Add GitHub Actions macOS
diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 3abba03..fed0181 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -25,4 +25,19 @@
     - name: 'Test'
       shell: bash
       run: |
-        ./gradlew --no-parallel build -x distTar
+        ./gradlew --no-parallel build
+
+  mac:
+    name: 'macOS (JDK 13)'
+    runs-on: macos-latest
+    steps:
+    - uses: actions/checkout@master
+      with:
+        fetch-depth: 50
+    - name: 'Set up JDK 13'
+      uses: actions/setup-java@v1
+      with:
+        java-version: 13
+    - name: 'Test'
+      run: |
+        ./gradlew --no-parallel build