Update .gitlab-ci.yml

.gitlab-ci.yml

@@ -1,5 +1,7 @@
 build_branch:
     image: docker.infra.flowdat.com/fd3/sf-php:latest
+    variables:
+      GIT_STRATEGY: clone
     script:
       - chmod 0600 keys/*
       - eval $(ssh-agent); ssh-add keys/gogs.drone.id_rsa