Actually make it compile

.github/workflows/gradle.yml

@@ -0,0 +1,18 @@
+name: Gradle
+
+on: [ push ]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v2
+      - name: Set up JDK 17
+        uses: actions/setup-java@v2
+        with:
+          distribution: temurin
+          java-version: 17
+          cache: gradle
+      - name: Build with Gradle
+        run: chmod a+x gradlew && ./gradlew build --no-daemon