code review 95560048: go.net/ipv4: add stubs for nacl build

ipv4/genericopt_stub.go

 // Copyright 2012 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.
 
-// +build plan9 solaris
+// +build nacl plan9 solaris
 
 package ipv4
 
 func (c *genericOpt) TOS() (int, error) {
         // TODO(mikio): Implement this
         return 0, errOpNoSupport
 }
 
 func (c *genericOpt) SetTOS(tos int) error {
         // TODO(mikio): Implement this
         return errOpNoSupport
 }
 
 func (c *genericOpt) TTL() (int, error) {
         // TODO(mikio): Implement this
         return 0, errOpNoSupport
 }
 
 func (c *genericOpt) SetTTL(ttl int) error {
         // TODO(mikio): Implement this
         return errOpNoSupport
 }