`cp -r /dev/urandom` copies content

The GNU cp command copies character devices as is if `-r` is specified:

```
# ls -l /dev/urandom
crw-rw-rw- 1 root root 1, 9 May 2 08:49 /dev/urandom
# gnucp -r /dev/urandom foo
# ls -l foo
crw-rw-r-- 1 root root 1, 9 Sep 20 15:38 foo
```

The uutils cp command tries to copy the content.

Bug-Ubuntu: https://bugs.launchpad.net/ubuntu/+source/rust-coreutils/+bug/2125263