Update .gitlab-ci.yml

.gitlab-ci.yml

+variables:
+  DOCKER_DRIVER: overlay2
+
 #image: python:alpine
 image: centos:latest
 
@@ -13,7 +16,7 @@ cache:
 
 stages:
   - step1
-  - step2
+  - build
   - deploy
 
 step1:
@@ -80,3 +83,14 @@ deploy to staging:
 #    - public
 #  only:
 #  - master
+
+build:
+    image: docker:19.03.11
+    stage: build
+    services:
+    - docker:19.03.11-dind
+    before_script:
+    - docker login -u $CI_REGISTRY_USER -p $CI_REGISTRY_PASSWORD $CI_REGISTRY
+    script:
+        - docker build --pull -t ${IMAGE_BUILD_TAG} -f Dockerfile --build-arg IMAGE_VERSION=${IMAGE_BUILD_TAG} .
+        - docker push ${IMAGE_BUILD_TAG}