Docker build fails

I am following the instructions [here](https://github.com/intel/linux-sgx/blob/master/docker/build/README.md) and docker build fails:

```
Creating build_aesm_1 ... error
compose.parallel.feed_queue: Pending: set()

ERROR: for build_aesm_1 Cannot start service aesm: error gathering device information while adding custom device "/dev/sgx/enclave": no such file or directory
compose.parallel.parallel_execute_iter: Failed:
compose.parallel.feed_queue: Pending: {}
compose.parallel.feed_queue: has upstream errors - not processing
compose.parallel.parallel_execute_iter: Failed:
compose.parallel.feed_queue: Pending: set()

ERROR: for aesm Cannot start service aesm: error gathering device information while adding custom device "/dev/sgx/enclave": no such file or directory
ERROR: compose.cli.main.exit_with_metrics: Encountered errors while bringing up the project.
```