Then use std.debug.warn?

Quoting the docs linked above:

> Usually you don't want to write to stdout. You want to write to stderr. And you don't care if it fails. It's more like a warning message that you want to emit. For that you can use a simpler API:

    const warn = @import("std").debug.warn;
    
    pub fn main() void {
        warn("Hello, world!\n");
    }