Sync Windows build flags between GYP and GN

build/config/win/BUILD.gn

 # 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.
 
 import("//build/config/win/visual_studio_version.gni")
 
 # Compiler setup for the Windows SDK. Applied to all targets.
 config("sdk") {
   # The include path is the stuff returned by the script.
   #include_dirs = msvc_config[0]  TODO(brettw) make this work.
@@ skipping 85 matching lines @@
 }
 
 # Subsystem --------------------------------------------------------------------
 
 # This is appended to the subsystem to specify a minimum version.
 if (current_cpu == "x64") {
   # The number after the comma is the minimum required OS version.
   # 5.02 = Windows Server 2003.
   subsystem_version_suffix = ",5.02"
 } else {
-  # Don't specify a min version on x86.
-  subsystem_version_suffix = ""
+  # 5.01 = Windows XP.
+  subsystem_version_suffix = ",5.01"
 }
 
 config("console") {
   ldflags = [ "/SUBSYSTEM:CONSOLE$subsystem_version_suffix" ]
 }
 config("windowed") {
   ldflags = [ "/SUBSYSTEM:WINDOWS$subsystem_version_suffix" ]
 }
 
 # Incremental linking ----------------------------------------------------------
@@ skipping 54 matching lines @@
 
 # Nominmax --------------------------------------------------------------------
 
 # Some third party code defines NOMINMAX before including windows.h, which
 # then causes warnings when it's been previously defined on the command line.
 # For such targets, this config can be removed.
 
 config("nominmax") {
   defines = [ "NOMINMAX" ]
 }