Update .gitlab-ci.yml

.gitlab-ci.yml

@@ -1,6 +1,12 @@
+image: alpine:3.9
+
 services:
   - docker:dind
 
+stages:
+  - build
+  - trigger
+
 variables:
   IMAGE_NAME: thallian/alpine-s6
 
@@ -18,7 +24,9 @@ build:
     - docker push $IMAGE_NAME:latest
 
 trigger:
+  stage: trigger
   script:
+    - apk --no-cache add curl
     - |
       for TRIGGER in $(echo $TRIGGERS | tr [:space:] ' '); do
         curl -fs -X POST -F ref=master -F token=${TRIGGER#*:} $CI_API_V4_URL/projects/${TRIGGER%:*}/trigger/pipeline > /dev/null