Add workflow to manually trigger a build (#1504)

.github/workflows/build.yml

@@ -0,0 +1,58 @@
+name: Manual Build
+
+on:
+  workflow_dispatch: # Enable manual run only
+
+jobs:
+  build:
+    # This job will run on ubuntu virtual machine
+    runs-on: ubuntu-latest
+    steps:
+
+      # Setup Java environment in order to build the Android app.
+      - uses: actions/checkout@v2
+      - uses: actions/setup-java@v2
+        with:
+          distribution: 'adopt'
+          java-version: '11'
+
+      # Setup the flutter environment.
+      - uses: subosito/flutter-action@v2
+        with:
+          channel: 'stable'
+          flutter-version: '3.13.4'
+
+      # Fetch sub modules
+      - run: git submodule update --init --recursive
+
+      # Get flutter dependencies.
+      - run: flutter pub get
+
+      - name: Setup keys
+        uses: timheuer/base64-to-file@v1
+        with:
+          fileName: 'keystore/ente_photos_key.jks'
+          encodedString: ${{ secrets.SIGNING_KEY }}
+
+      # Build independent apk.
+      - name: Build
+        run: flutter build apk --release --flavor independent && mv build/app/outputs/flutter-apk/app-independent-release.apk build/app/outputs/flutter-apk/ente.apk
+        env:
+          SIGNING_KEY_PATH: '/home/runner/work/_temp/keystore/ente_photos_key.jks'
+          SIGNING_KEY_ALIAS: ${{ secrets.SIGNING_KEY_ALIAS }}
+          SIGNING_KEY_PASSWORD: ${{ secrets.SIGNING_KEY_PASSWORD }}
+          SIGNING_STORE_PASSWORD: ${{ secrets.SIGNING_STORE_PASSWORD }}
+
+      - name: Checksum
+        run: sha256sum build/app/outputs/flutter-apk/ente.apk > build/app/outputs/flutter-apk/sha256sum
+
+      # Upload generated apk to the artifacts.
+      - uses: actions/upload-artifact@v2
+        with:
+          name: release-apk
+          path: build/app/outputs/flutter-apk/ente.apk
+
+      - uses: actions/upload-artifact@v2
+        with:
+          name: release-checksum
+          path: build/app/outputs/flutter-apk/checksum