Fix build break when building with enable_openvr=true on Windows

third_party/openvr/BUILD.gn

 # Copyright 2017 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.
 
-loadable_module("openvr") {
+component("openvr") {
   output_name = "openvr_api"
 
   # Some ascii versions of Windows APIs are used in this code.
   configs -= [ "//build/config/win:unicode" ]
 
   # This code can be built using internal OpenVR functionality, but the internal
   # dependencies aren't available to us.
   defines = [ "VR_API_PUBLIC" ]
 
   sources = [
     "src/src/jsoncpp.cpp",
     "src/src/openvr_api_public.cpp",
     "src/src/vrcommon/dirtools_public.cpp",
     "src/src/vrcommon/envvartools_public.cpp",
     "src/src/vrcommon/hmderrors_public.cpp",
     "src/src/vrcommon/pathtools_public.cpp",
     "src/src/vrcommon/sharedlibtools_public.cpp",
     "src/src/vrcommon/strtools_public.cpp",
     "src/src/vrcommon/vrpathregistry_public.cpp",
   ]
 
+  if (target_cpu == "x64" && is_win) {
+    defines += [ "WIN64" ]
+  }
+
   include_dirs = [
     "src/headers",
     "src/src",
     "src/src/json",
     "src/src/vrcommon",
   ]
 }