Do not call stty on non-tty

When testing on a non-tty (e.g.: github actions),
either one of these lines produces an error:

```ruby
input.echo = true
ask("question", "y") { |q| q.readline = true }
```

The error is produced by ruby internals:

```bash
echo | rake | cat

......stty: stdin isn't a terminal......
```

This change skips the stty calls if the input is not on a tty, so the
errors will not be produced.

0 files changed, 0 insertions, 0 deletions