Add build defensive for riscv64 files

internal/socket/sys_linux_riscv64.go

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// +build riscv64
+
 package socket
 
 const (

internal/socket/zsys_linux_riscv64.go

@@ -1,6 +1,8 @@
 // Code generated by cmd/cgo -godefs; DO NOT EDIT.
 // cgo -godefs defs_linux.go
 
+// +build riscv64
+
 package socket
 
 const (

ipv4/zsys_linux_riscv64.go

@@ -1,6 +1,8 @@
 // Code generated by cmd/cgo -godefs; DO NOT EDIT.
 // cgo -godefs defs_linux.go
 
+// +build riscv64
+
 package ipv4
 
 const (

ipv6/zsys_linux_riscv64.go

@@ -1,6 +1,8 @@
 // Code generated by cmd/cgo -godefs; DO NOT EDIT.
 // cgo -godefs defs_linux.go
 
+// +build riscv64
+
 package ipv6
 
 const (