Update drone.yml

drone.yml

   os: linux
   arch: amd64
 
+cache:
+  mount:
+    - /var/cache/apt/archives
+
 steps:
 - name: build
   image: debian:stable-slim
   when:
     branch: master
     event: tag
-
-cache:
-  mount:
-    - /var/cache/apt/archives
-