Update dependencies and add auto-build

.gitlab-ci.yml

+build:
+  stage: build
+  image:
+    name: gcr.io/kaniko-project/executor:debug
+    entrypoint: [""]
+  script:
+    - mkdir -p /kaniko/.docker
+    - echo "{\"auths\":{\"$CI_REGISTRY\":{\"username\":\"$CI_REGISTRY_USER\",\"password\":\"$CI_REGISTRY_PASSWORD\"}}}" > /kaniko/.docker/config.json
+    - /kaniko/executor --context $CI_PROJECT_DIR --dockerfile $CI_PROJECT_DIR/Dockerfile --destination $CI_REGISTRY_IMAGE:${CI_COMMIT_TAG:-$CI_COMMIT_SHORT_SHA}

Dockerfile

-ARG SDK_VERSION=30.0.3
-FROM k8r.eu/justjanne/android-sdk:$SDK_VERSION
+FROM k8r.eu/justjanne/android-sdk:latest
 RUN apt-get --quiet update --yes && \
     apt-get --quiet install --yes python3 python3-lxml