tty: support building for Windows as a utility just showing "CON"

[oech3]

[ChrisDenton]

Canonically it should be \\.\CON. The name CON on its own is ambiguous with a file in the current directory with that name.

[oech3]

Done. (This might cause some confusion for MSYS)

[ChrisDenton]

For msys2, the best thing we can reasonably do is return the filename of the handle if it's a msys pipe. In the standard library we check first that it's a named pipe and second that it has a name starting with msys- or cygwin-. https://github.com/rust-lang/rust/blob/0424cc16731e6141a18077f8ccde77ba148d9649/library/std/src/sys/io/is_terminal/windows.rs#L25

This isn't ideal. It's of course possible for anyone to make a pipe with a name that fits the pattern. But it's currently the best way we've found of reliably detecting an msys2 terminal.

[oech3]

Any idea for hostid and nice?