Recognize NetBSD as a Host OS

tools/gn/args.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "tools/gn/args.h"
 
 #include "base/sys_info.h"
 #include "build/build_config.h"
 #include "tools/gn/variables.h"
 
@@ skipping 240 matching lines @@
   // Host OS.
   const char* os = nullptr;
 #if defined(OS_WIN)
   os = "win";
 #elif defined(OS_MACOSX)
   os = "mac";
 #elif defined(OS_LINUX)
   os = "linux";
 #elif defined(OS_ANDROID)
   os = "android";
+#elif defined(OS_NETBSD)
+  os = "netbsd";
 #else
   #error Unknown OS type.
 #endif
 
   // Host architecture.
   static const char kX86[] = "x86";
   static const char kX64[] = "x64";
   static const char kArm[] = "arm";
   static const char kMips[] = "mipsel";
   const char* arch = nullptr;
@@ skipping 75 matching lines @@
     Scope* scope) const {
   lock_.AssertAcquired();
   return declared_arguments_per_toolchain_[scope->settings()];
 }
 
 Scope::KeyValueMap& Args::OverridesForToolchainLocked(
     Scope* scope) const {
   lock_.AssertAcquired();
   return toolchain_overrides_[scope->settings()];
 }