tty: add missing newline to output

[ChrisX101010]

Fixes #10239

[ChrisDryden]

(/bin/tty >&- 2>/dev/null); echo $?

This command shows what happens when theres an error in writing to stdout, the error code that GNU is expecting is 3, but by adding that ? it will make it handled and return a 1. You can get around this by doing:

Ok(name) => stdout
    .write_all_os(name.as_os_str())
    .and_then(|_| writeln!(stdout)),

[oech3]

target/debug/tty > /dev/full silently returns 3. But GNU have tty: write error: No space left on device.

[ChrisX101010]

@ChrisDryden can you check now, sir? thank you!

[oech3]

Would you add test to check newline (and exit code of >/dev/full if possible ) to
https://github.com/uutils/coreutils/blob/main/tests/by-util/test_tty.rs ? Thankyou.

[github-actions]

GNU testsuite comparison:

Note: The gnu test tests/basenc/bounded-memory is now being skipped but was previously passing.