Update workflow

.github/workflows/gradle.yml

@@ -1,18 +1,26 @@
-name: Gradle
-
-on: [ push ]
+# Adapted from Paper's build script
+name: Build
+on: [push, pull_request]
 
 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
+    build:
+        # 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 }}
+        runs-on: ubuntu-latest
+        strategy:
+            matrix:
+                java: [17]
+            fail-fast: true
+        steps:
+            - uses: actions/checkout@v2.4.0
+            - name: JDK ${{ matrix.java }}
+              uses: actions/setup-java@v3.1.0
+              with:
+                  java-version: ${{ matrix.java }}
+                  cache: 'gradle'
+                  distribution: 'temurin'
+            - name: Build
+              run: |
+                  git config --global user.email "no-reply@github.com"
+                  git config --global user.name "Github Actions"
+                  ./gradlew build --stacktrace