Add some more libjingle targets to the GN build.

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.
 
   defines = [
     "_ATL_NO_OPENGL",
-    "_WIN32_WINNT=0x0602",
     "_WINDOWS",
     "CERT_CHAIN_PARA_HAS_EXTRA_FIELDS",
     "NTDDI_VERSION=0x06020000",
     "PSAPI_VERSION=1",
     "WIN32",
-    "WINVER=0x0602",
   ]
 
   include_dirs = system_include_dirs
 
   if (is_visual_studio_express) {
     # https://code.google.com/p/chromium/issues/detail?id=372451#c20
     # Warning 4702 ("Unreachable code") should be re-enabled once Express users
     # are updated to VS2013 Update 2.
     cflags = [ "/wd4702" ]
   } else {
     # Only supported on non-Express versions.
     defines += [ "_SECURE_ATL" ]
   }
 }
 
+# Sets the default Windows build version. This is separated because some
+# targets need to manually override it for their compiles.
+config("winver") {
+  defines = [
+    "_WIN32_WINNT=0x0602",
+    "WINVER=0x0602",
+  ]
+}
+
 # Linker flags for Windows SDK setup, this is applied only to EXEs and DLLs.
 config("sdk_link") {
   if (cpu_arch == "x64") {
     ldflags = [ "/MACHINE:X64" ]
     lib_dirs = [
       "$windows_sdk_path\Lib\win8\um\x64",
       "$visual_studio_path\VC\lib\amd64",
       "$visual_studio_path\VC\atlmfc\lib\amd64",
     ]
     if (is_visual_studio_express) {
@@ skipping 106 matching lines @@
 
 # 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",
   ]
 }