ci: Use DOCKER_BUILDKIT for lint image

Can be reviewed with:
--color-moved=dimmed-zebra  --ignore-all-space

.cirrus.yml

@@ -70,7 +70,7 @@ task:
   # For faster CI feedback, immediately schedule the linters
   << : *CREDITS_TEMPLATE
   python_cache:
-    folder: "/tmp/python"
+    folder: "/python_build"
     fingerprint_script: cat .python-version /etc/os-release
   unshallow_script:
     - git fetch --unshallow --no-tags