add clean pipeline

.drone.yml

@@ -35,3 +35,39 @@ volumes:
 - name: android
   host: 
     path: /home/drone/Android/Sdk
+
+trigger:
+  branch:
+    exclude:
+    - master
+
+---
+kind: pipeline
+type: docker
+name: clean
+
+steps:
+- name: build 
+  image: nextcloudci/android:android-49
+  commands:
+  - ./gradlew build
+
+- name: notify
+  image: appleboy/drone-telegram
+  settings:
+    token:
+      from_secret: telegram_token
+    to:
+      from_secret: telegram_user
+    format: markdown
+    message: |
+      Build [#{{build.number}}]({{build.link}}) from commit [{{truncate commit.sha 10}}]({{commit.link}}) on {{commit.branch}} **failed**.
+      {{uppercasefirst commit.author}} please fix me!
+  when:
+    status:
+      - failure
+
+trigger:
+  branch:
+    include:
+    - master