gyp: update xml string encoding conversion

Bug: nodejs/node-gyp#1203
Change-Id: I30d71a2bb3d4b09e7bd9409c3c45c32bd182d736
Reviewed-on: https://chromium-review.googlesource.com/509632
Commit-Queue: Mark Mentovai <mark@chromium.org>
Reviewed-by: Mark Mentovai <mark@chromium.org>

pylib/gyp/easy_xml.py

@@ -4,6 +4,7 @@
 
 import re
 import os
+import locale
 
 
 def XmlToString(content, encoding='utf-8', pretty=False):
@@ -116,6 +117,10 @@ def WriteXmlIfChanged(content, path, encoding='utf-8', pretty=False,
   if win32 and os.linesep != '\r\n':
     xml_string = xml_string.replace('\n', '\r\n')
 
+  default_encoding = locale.getdefaultlocale()[1]
+  if default_encoding and default_encoding.upper() != encoding.upper():
+    xml_string = xml_string.decode(default_encoding).encode(encoding)
+
   # Get the old content
   try:
     f = open(path, 'r')