net: fix build on netbsd

Change-Id: Ia5c6d9fb114be65d7c20c7eb97ed696977051031
Reviewed-on: https://go-review.googlesource.com/11167Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/net/cgo_resnew.go

@@ -3,7 +3,7 @@
 // license that can be found in the LICENSE file.
 
 // +build cgo,!netgo
-// +build darwin linux solaris
+// +build darwin linux netbsd solaris
 
 package net
 

src/net/cgo_resold.go

@@ -3,7 +3,7 @@
 // license that can be found in the LICENSE file.
 
 // +build cgo,!netgo
-// +build freebsd dragonfly netbsd openbsd
+// +build freebsd dragonfly openbsd
 
 package net