Merge branch 'zj-faster-image-trigger-builds' into 'master'

Use smaller image when triggering a build

See merge request !11674

.gitlab-ci.yml

@@ -150,6 +150,7 @@ stages:
 # Trigger a package build on omnibus-gitlab repository
 
 build-package:
+  image: ruby:2.3-alpine
   before_script: []
   services: []
   variables: