Fix GN unit tests on Windows, GN x64 build.

sandbox/win/BUILD.gn

 # Copyright 2014 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.
 
 import("//testing/test.gni")
 
 source_set("sandbox") {
   sources = [
     "src/acl.cc",
     "src/acl.h",
@@ skipping 144 matching lines @@
       "src/sidestep/mini_disassembler.cpp",
       "src/sidestep/mini_disassembler.h",
       "src/sidestep/preamble_patcher_with_stub.cpp",
       "src/sidestep/preamble_patcher.h",
       "src/Wow64.cc",
       "src/Wow64.h",
     ]
   }
 
   deps = [
-    ":copy_wow_helper",
     "//base",
   ]
+  if (cpu_arch == "x86") {
+    deps += [ ":copy_wow_helper" ]
+  }
 }
 
 if (cpu_arch == "x86") {
   # Make a target that copies the wow_helper files to the out dir.
   #
   # TODO(brettw) we can probably just build this now that we have proper
   # toolchain support.
   copy("copy_wow_helper") {
     sources = [
       "wow_helper/wow_helper.exe",
@@ skipping 112 matching lines @@
     "sandbox_poc/pocdll/network.cc",
     "sandbox_poc/pocdll/pocdll.cc",
     "sandbox_poc/pocdll/processes_and_threads.cc",
     "sandbox_poc/pocdll/registry.cc",
     "sandbox_poc/pocdll/spyware.cc",
     "sandbox_poc/pocdll/utils.h",
   ]
 
   defines = [ "POCDLL_EXPORTS" ]
 }