Windows CI: Turning off pkg\symlink unit testing

Signed-off-by: John Howard <jhoward@microsoft.com>

symlink/fs_unix_test.go

@@ -1,3 +1,5 @@
+// +build !windows
+
 // Licensed under the Apache License, Version 2.0; See LICENSE.APACHE
 
 package symlink
@@ -10,6 +12,9 @@ import (
 	"testing"
 )
 
+// TODO Windows: This needs some serious work to port to Windows. For now,
+// turning off testing in this package.
+
 type dirOrLink struct {
 	path   string
 	target string