.gitlab-ci.yml: Moving code_quality job into tests phase

This job always takes a long time and does not really depend
on the artifacts in the 'test' phase, moving it to the 'test'
phase will reduce overall CI time.

.gitlab-ci.yml

@@ -153,15 +153,11 @@ docs:
     - public/
 
 
-#####################################################
-#                    Post stage                     #
-#####################################################
-
 # Check code quality with gitlab's built-in feature.
 #
 code_quality:
   image: docker:stable
-  stage: post
+  stage: test
   variables:
     DOCKER_DRIVER: overlay2
   allow_failure: true
@@ -177,6 +173,10 @@ code_quality:
   artifacts:
     paths: [gl-code-quality-report.json]
 
+#####################################################
+#                    Post stage                     #
+#####################################################
+
 analysis:
   stage: post
   script: