os: do not forget to set ModeDevice when using ModeCharDevice

Fixes #23123

Change-Id: Ia4ac947cc49ef3d150ef60a095b86552dcef397d
Reviewed-on: https://go-review.googlesource.com/84435Reviewed-by: Giovanni Bajo <rasky@develer.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Giovanni Bajo <rasky@develer.com>

src/os/os_test.go

@@ -1881,7 +1881,7 @@ func TestStatStdin(t *testing.T) {
 		t.Fatal(err)
 	}
 	switch mode := fi.Mode(); {
-	case mode&ModeCharDevice != 0:
+	case mode&ModeCharDevice != 0 && mode&ModeDevice != 0:
 	case mode&ModeNamedPipe != 0:
 	default:
 		t.Fatalf("unexpected Stdin mode (%v), want ModeCharDevice or ModeNamedPipe", mode)

src/os/types_windows.go

@@ -48,7 +48,7 @@ func (fs *fileStat) Mode() (m FileMode) {
 	case syscall.FILE_TYPE_PIPE:
 		m |= ModeNamedPipe
 	case syscall.FILE_TYPE_CHAR:
-		m |= ModeCharDevice
+		m |= ModeDevice | ModeCharDevice
 	}
 	return m
 }