Add support for 32-bit and 64-bit Windows compiles in GN.

tools/gn/variables.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/variables.h"
 
 namespace variables {
 
 // Built-in variables ----------------------------------------------------------
 
@@ skipping 22 matching lines @@
 const char kCpuArch_Help[] =
     "cpu_arch: Current processor architecture.\n"
     "\n"
     "  The initial value is based on the current architecture of the host\n"
     "  system. However, the build configuration can set this to any value.\n"
     "\n"
     "  This value is not used internally by GN for any purpose, so you can\n"
     "  set it to whatever value is relevant to your build.\n"
     "\n"
     "Possible initial values set by GN:\n"
-    "  - \"ia32\"\n"
-    "  - \"ia64\"\n"
+    "  - \"x86\"\n"
+    "  - \"x64\"\n"
     "  - \"arm\"\n";
 
 const char kCurrentToolchain[] = "current_toolchain";
 const char kCurrentToolchain_HelpShort[] =
     "current_toolchain: [string] Label of the current toolchain.";
 const char kCurrentToolchain_Help[] =
     "current_toolchain: Label of the current toolchain.\n"
     "\n"
     "  A fully-qualified label representing the current toolchain. You can\n"
     "  use this to make toolchain-related decisions in the build. See also\n"
@@ skipping 760 matching lines @@
     INSERT_VARIABLE(Script)
     INSERT_VARIABLE(SourcePrereqs)
     INSERT_VARIABLE(Sources)
   }
   return info_map;
 }
 
 #undef INSERT_VARIABLE
 
 }  // namespace variables