add vendoring

vendor/golang.org/x/sys/cpu/cpu_loong64.go

@@ -0,0 +1,13 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build loong64
+// +build loong64
+
+package cpu
+
+const cacheLineSize = 64
+
+func initOptions() {
+}