toolbox: add hgfs freebsd stub

The toolbox/process package uses a few hgfs package constants.
Need stub this to compile when GOOS=freebsd

toolbox/hgfs/hgfs_freebsd.go

@@ -0,0 +1,24 @@
+/*
+Copyright (c) 2021 VMware, Inc. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package hgfs
+
+import (
+	"os"
+)
+
+func (a *AttrV2) sysStat(info os.FileInfo) {
+}