Add check for top-level ee directory in CE repo

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

.gitlab-ci.yml

@@ -836,3 +836,15 @@ gitlab_git_test:
   cache: {}
   script:
     - spec/support/prepare-gitlab-git-test-for-commit --check-for-changes
+
+no_ee_check:
+  <<: *dedicated-runner
+  <<: *except-docs-and-qa
+  variables:
+    SETUP_DB: "false"
+  before_script: []
+  cache: {}
+  script:
+    - scripts/no-ee-check
+  only:
+    - //@gitlab-org/gitlab-ce

scripts/no-ee-check

@@ -0,0 +1,8 @@
+#!/usr/bin/env ruby
+ee_path = File.join(File.expand_path(File.dirname(__FILE__)), '../ee')
+result = Dir.exist?(ee_path)
+
+if result
+  puts 'The repository contains /ee directory. There should be no /ee directory in CE repo.'
+  exit 1
+end