Make GITLAB_FEATURES in build_spec compatible with EE

Right now this fails in EE since the EE codebase defaults to having a starter license which means there are features in this value. This seems to be incompatible with the statement that tests should behave the same in CE as EE but I think that since there is a before on all EE specs creating a starter license it unfortunately does not behave that way.
This is needed for #40994 and fixes the failing specs in https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/4393

spec/models/ci/build_spec.rb

@@ -1413,7 +1413,7 @@ describe Ci::Build do
       [
         { key: 'CI', value: 'true', public: true },
         { key: 'GITLAB_CI', value: 'true', public: true },
-        { key: 'GITLAB_FEATURES', value: '', public: true },
+        { key: 'GITLAB_FEATURES', value: project.namespace.features.join(','), public: true },
         { key: 'CI_SERVER_NAME', value: 'GitLab', public: true },
         { key: 'CI_SERVER_VERSION', value: Gitlab::VERSION, public: true },
         { key: 'CI_SERVER_REVISION', value: Gitlab::REVISION, public: true },