Image build is optimized.

.gitlab-ci.yml

@@ -25,12 +25,12 @@ build:
   before_script:
     - export DOCKER_TMPDIR=/mnt/volume
     - docker system prune -a -f
+    - docker volume prune -f
     - df -h
+    - ls -la /mnt/volume
   script:
     - docker build --no-cache --pull --progress=plain -t flask-backend-full -f flask_ml_api/Dockerfile .
-
   cache:
     key: build-cache
     paths:
       - /mnt/volume
-