Add note about Docker socket mounting

When using `docker:dind` service and the Runner has the socket mounted
as well it will lead to the following error:

```
Failed to load listeners: can't create unix socket /var/run/docker.sock:
device or resource busy
```

reference https://gitlab.com/gitlab-org/gitlab-ce/issues/63418

doc/ci/docker/using_docker_build.md

@@ -205,7 +205,14 @@ An example project using this approach can be found here: <https://gitlab.com/gi
 
 ### Use Docker socket binding
 
-The third approach is to bind-mount `/var/run/docker.sock` into the container so that docker is available in the context of that image.
+The third approach is to bind-mount `/var/run/docker.sock` into the
+container so that Docker is available in the context of that image.
+
+NOTE: **Note:**
+If you bind the Docker socket [when using GitLab Runner 11.11 or
+newer](https://gitlab.com/gitlab-org/gitlab-runner/merge_requests/1261),
+you can no longer use `docker:dind` as a service because volume bindings
+are done to the services as well, making these incompatible.
 
 In order to do that, follow the steps: