Refactor for Sync method (#3426)

weed/storage/backend/disk_file_others.go

@@ -0,0 +1,9 @@
+//go:build !linux && !darwin
+// +build !linux,!darwin
+
+package backend
+
+// Using default sync operation
+func (df *DiskFile) Sync() error {
+	return df.File.Sync()
+}