Update .gitlab-ci.yml

.gitlab-ci.yml

@@ -5,13 +5,16 @@ default:
       - ./bin/slime_d
     expire_in: 1 week
 
+variables:
+  GIT_SUBMODULE_STRATEGY: recursive
+
 stages:
   - build_debug
   - build_release
   - test
 
 build_clang++_d:
-  
+  image: warchantua/dev-essential
   stage: build_debug
   script:
     - ls ./3rd/ftb