Github Actions: Try to generate nightly nbms

.github/workflows/gradle.yml

@@ -0,0 +1,35 @@
+name: Nightly Generation
+
+on:
+  push:
+    branches: [ master ]
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up JDK 11
+      uses: actions/setup-java@v1
+      with:
+        java-version: 11
+    - name: Grant execute permission for gradlew and others.
+      run: chmod +x gradlew *.sh
+      
+    - name: Download the Engine
+      run: ./build_engine.sh
+      
+    - name: Fix the Engine
+      run: ./fix_engine.sh
+      
+    - name: Build
+      run: ./gradlew buildSdk
+      
+    - name: Build Nightly NBMs
+      env:
+        NBM_SIGN_PASS: ${{ secrets.NBM_SIGN_PASS }}
+      # For Stable, use set-spec-version
+      run: ant -Dstorepass="$NBM_SIGN_PASS" set-impl-version suite.nbms unset-impl-version
+  
+    - name: List potential artifacts
+      run: ls -lsh build/ && ls -lsh build/updates