isatty syscall sometimes does not return the correct error

[Kyota-exe]

The isatty system call currently returns ENOTTY even when fd is not a valid file descriptor. It should be returning EBADF in this case (although I doubt any programs really care).

This should be an easy fix by just returning whatever error is returned by ioctl instead of returning ENOTTY unconditionally when the TIOCGWINSZ fails.

I can take this one if you can assign me to the issue :)

[48cf]

Sure thing!