pkg: Fix dir permission check on Windows

pkg/fileutil/dir_unix.go

@@ -18,5 +18,10 @@ package fileutil
 
 import "os"
 
+const (
+	// PrivateDirMode grants owner to make/remove files inside the directory.
+	PrivateDirMode = 0700
+)
+
 // OpenDir opens a directory for syncing.
 func OpenDir(path string) (*os.File, error) { return os.Open(path) }