Windows: stderr output leaks into stdout

[qweeah]

I found that on Windows, if a console is generated from stderr, output sent towards the console will go into stdout with extra warning like failed to get console mode for stdout: The handle is invalid.(resovled in 7b7885a).

Verified this with a simple test program in here which simply outputs three messages

// 1. generate console from stderr
c, err := console.ConsoleFromFile(os.Stderr)
if err != nil {
fmt.Println("failed to generate console from stderr", err)
os.Exit(1)
}

// 2. output to stderr, stdout and console
fmt.Fprintln(os.Stderr, "via os.Stderr")
fmt.Fprintln(os.Stdout, "via os.Stdout")
fmt.Fprintln(c, "via stderr console")

In Powershell, the output is like:

> $a=.\console.exe
via os.Stderr     
> $a
failed to get console mode for stdout: The handle is invalid.
via os.Stdout
via stderr console    

The via stderr console log goes wrongly into the variable $a (which should only contain the command's success output stream and stdout output).

As a comparison, below is the behavior of the test program on Zsh(Ubuntu 20.04)

> a=$(./console)
via os.Stderr
via stderr console
> echo $a
via os.Stdout

We can see tht the via stderr console doesn't goes into the stdout output as expected.

[qweeah]

BTW I am using github.com/containerd/console v1.0.3