ci: create cache dir before testing

.gitlab-ci.yml

@@ -24,6 +24,7 @@ run_test_cases:
   before_script:
     - *install_requirements
     - cp config/engine-tests.yaml config/engine.yaml
+    - mkdir -p .cache
   script:
     - make coverage
   coverage: '/(?i)total.*? (100(?:\.0+)?\%|[1-9]?\d(?:\.\d+)?\%)$/'