Add gitlab ci

second try

.gitlab-ci.yml

@@ -8,10 +8,14 @@ build-gcc7:
   stage: build
   image: ubuntu:16.04
   tags: [docker]
+  services:
+    - docker:dind
   variables:
     CXX: g++-8
     CC: gcc-8
     TRAVIS_OS_NAME: linux
+    DOCKER_HOST:tcp://docker:2375/
+    #DOCKER_TLS_CERTDIR:
   before_script:
     - apt-get update
     - apt-get install -y software-properties-common