Try fixing dind support

This is just a guess.

Currently builds are failing with,

Cannot connect to the Docker daemon at tcp://docker:2375. Is the docker daemon running?
Cannot connect to the Docker daemon at tcp://docker:2375. Is the docker daemon running?

Fixes #1 (closed).

.gitlab-ci.yml

-image: docker:stable
+image: docker:19.03.1
 
 stages:
   - lint
   - build
 
 services:
-  - docker:dind
+  - docker:19.03.1-dind
 
 variables:
   CONTAINER_IMAGE_BASE: registry.gitlab.haskell.org/$CI_PROJECT_PATH
-  DOCKER_HOST: tcp://docker:2375
   DOCKER_DRIVER: overlay2
+  DOCKER_TLS_CERTDIR: "/certs"
 
 lint:
   stage: lint
@@ -28,6 +28,8 @@ lint:
   only:
    - master
    - merge_requests
+  before_script:
+    - docker info
   script:
     - |
       CONTAINER_IMAGE="$CONTAINER_IMAGE_BASE/$IMAGE"