How to write POSIX text files under Windows?

Help!
1

I can’t see how to override the default
stream_property(S, newline(dos))
when (or after) opening a file for writing text (8.0.3 Windows)

2

What is wrong with this?

open(File, write, Out),
set_stream(Out, newline(posix)).
3

Thx - I should have known about, or found, that :-/