build the Dockerimage used in CI

.gitlab-ci.yml

-image: quantumtinkerer/research # until the other image is build
+image: gitlab.kwant-project.org:5005/qt/adaptive:latest
 
 stages:
   - prebuild
@@ -10,7 +10,7 @@ build docker:
     name: gcr.io/kaniko-project/executor:debug
     entrypoint: [""]
   before_script:
-    - docker login -u $CI_DEPLOY_USER -p $CI_DEPLOY_PASSWORD $CI_REGISTRY
+    - echo "{\"auths\":{\"$CI_REGISTRY\":{\"username\":\"$CI_REGISTRY_USER\",\"password\":\"$CI_REGISTRY_PASSWORD\"}}}" > /kaniko/.docker/config.json
     - export CI_REF=${CI_COMMIT_TAG:-latest}
   script:
     - /kaniko/executor