build container image in Gitlab CI/CD

.gitlab-ci.yml

+build:
+  image:
+    name: gcr.io/kaniko-project/executor:debug
+    entrypoint: [""]
+  script:
+    - 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:latest"