build: Move to using Indra

.github/workflows/gradle.yml

@@ -1,20 +1,24 @@
 # This workflow will build a Java project with Maven
 # For more information see: https://help.github.com/actions/language-and-framework-guides/building-and-testing-java-with-maven
 
-name: Java CI with Maven
+name: Java CI with Gradle
 
 on: [ push, pull_request ]
 
 jobs:
   build:
-
-    runs-on: ubuntu-latest
-
+    # Only run on PRs if the source branch is on someone else's repo
+    if: ${{ github.event_name != 'pull_request' || github.repository != github.event.pull_request.head.repo.full_name }}
+    strategy:
+      matrix:
+        os: ["ubuntu-latest", "windows-latest"]
+    runs-on: "${{ matrix.os }}"
     steps:
       - uses: actions/checkout@v2
-      - name: Set up JDK 1.8
+      - uses: gradle/wrapper-validation-action@v1
+      - name: Set up JDK 11
         uses: actions/setup-java@v1
         with:
-          java-version: 1.8
+          java-version: 11
       - name: Build with Gradle
         run: ./gradlew clean build