The output from GNU Core Utilities dd is different in apline and ubuntu

[薛帅]

Dear all,

For convenience, I test the following command with docker.

In Ubuntu 18.04.1 LTS, the `dd` command output three lines.
```
dd if=/dev/zero of=/tmp/out bs=512 count=10
10+0 records in
10+0 records out
5120 bytes (5.1 kB, 5.0 KiB) copied, 6.6846e-05 s, 76.6 MB/s
```

While in apline 3.9.0, the `dd` command output only two lines.
``` 
dd if=/dev/zero of=/tmp/out bs=512 count=10
10+0 records in
10+0 records out
```

Any idea about it?

Thank you.