Update .gitlab-ci.yml

.gitlab-ci.yml

-
-image: debian
-
-build:
+# This file is a template, and might need editing before it works on your project.
+docker-build-master:
+  # Official docker image.
+  image: docker:latest
+  stage: build
+  services:
+    - docker:dind
   before_script:
-   - apt update
-   - apt install libsimavr-dev avrdude avra libelf-dev arduino-mk gcc-avr avr-libc
-
+    - docker login -u "$CI_REGISTRY_USER" -p "$CI_REGISTRY_PASSWORD" $CI_REGISTRY
   script:
-    - make
-
-test:
-  stage: test
-  script:
-    - ./test.sh
+    - docker build --pull -t "$CI_REGISTRY_IMAGE" .
+    - docker push "$CI_REGISTRY_IMAGE"
+  only:
+    - master