vfs: make mount tests run on OpenBSD

vfs/vfstest/write.go

@@ -5,6 +5,7 @@ import (
 	"runtime"
 	"testing"
 
+	"github.com/rclone/rclone/vfs"
 	"github.com/rclone/rclone/vfs/vfscommon"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -110,6 +111,9 @@ func TestWriteFileDup(t *testing.T) {
 
 	var dupFd uintptr
 	dupFd, err = writeTestDup(fh.Fd())
+	if err == vfs.ENOSYS {
+		t.Skip("dup not supported on this platform")
+	}
 	require.NoError(t, err)
 
 	dupFile := os.NewFile(dupFd, fh.Name())

vfs/vfstest/write_other.go

@@ -1,4 +1,4 @@
-//go:build !linux && !darwin && !freebsd && !windows
+//go:build !linux && !darwin && !freebsd && !openbsd && !windows
 
 package vfstest
 

vfs/vfstest/write_unix.go

@@ -1,4 +1,4 @@
-//go:build linux || darwin || freebsd
+//go:build linux || darwin || freebsd || openbsd
 
 package vfstest