ci: create folder before building

Author: vmarchaud

.drone.yml

@@ -32,6 +32,7 @@ pipeline:
     image: node:8
     commands:
       - npm install 2> /dev/null
+      - mkdir dist
       - npm run build
       - npm run dist
     when:
@@ -46,4 +47,4 @@ matrix:
     - 4
     - 6
     - 7
-    - 8
+    - 8