use a docker in docker runner

.gitlab-ci.yml

@@ -3,7 +3,15 @@ stages:
   - deploy
 
 build:
-  image: ubuntu
+  image: docker:stable
+
+  variables:
+    DOCKER_HOST: tcp://docker:2375/
+    DOCKER_DRIVER: overlay2
+
+ services:
+   - docker:dind
+
   stage: build
   tags:
     - build_tes