Add github actions for CI build.

.github/workflows/gradle.yml

@@ -0,0 +1,36 @@
+# This workflow uses actions that are not certified by GitHub.
+# They are provided by a third-party and are governed by
+# separate terms of service, privacy policy, and support
+# documentation.
+# This workflow will build a Java project with Gradle and cache/restore any dependencies to improve the workflow execution time
+# For more information see: https://help.github.com/actions/language-and-framework-guides/building-and-testing-java-with-gradle
+
+name: Build
+
+on:
+  push:
+    branches: [ rv6-1.12 ]
+  pull_request:
+    branches: [ rv6-1.12 ]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up JDK 8
+      uses: actions/setup-java@v2
+      with:
+        java-version: '8'
+        distribution: 'temurin'
+    - name: Build with Gradle
+      uses: gradle/gradle-build-action@4137be6a8bf7d7133955359dbd952c0ca73b1021
+      with:
+        arguments: build
+    - name: Upload artifacts & release assets
+      uses: nanoufo/action-upload-artifacts-and-release-assets@v1.4
+      with:
+        # A file or wildcard pattern that describes what to upload
+        path: build/libs/*.jar