tasklog: detect Cygwin-style pipe TTYs as TTYs as well

Some Unix emulation layers for Windows, such as Cygwin and MSYS, use
pipes to create their Unix-style TTYs. These TTYs are not detected as
such by Windows, which sees them as pipes. However, our isatty module
has a way to detect them, and they will function just like a TTY for our
purposes, so check for them as well and handle them as TTYs if present.

tasklog/log.go

@@ -98,7 +98,7 @@ type hasFd interface {
// tty returns true if the writer is connected to a tty
func tty(writer io.Writer) bool {
	if v, ok := writer.(hasFd); ok {
		return isatty.IsTerminal(v.Fd())
		return isatty.IsTerminal(v.Fd()) || isatty.IsCygwinTerminal(v.Fd())
	}
	return false
}