lib, gyp: add support for non-eanglish letters in pathes

On Windows 10 i discovered an issue that if there are
non-english letters or symbols in path
for python find-python.js script can't find it.
This bug is couse by encoding issue which
I have (i hope) fixed. At least this bug fix works for me.

Have changed:
       modified:   gyp/pylib/gyp/easy_xml.py
         python 2.7 handle xml_string in wrong way
         becouse of encoding (line 128)
       modified:   gyp/pylib/gyp/input.py
         if "encoding:utf8" on line 240 doesn't marked cause to error
       new file:   lib/find-python-script.py
         i have created this file for convience.
         Script which can handle non-eanglish
         letters and symbols cann't °fit one lne
         becouse it is necessary to specify
         instarctions for several versions of python
       modified:   lib/find-python.js
         to make js understand python (line 249)

Author: owl-from-hogvarts

gyp/pylib/gyp/easy_xml.py

@@ -2,6 +2,7 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import sys
 import re
 import os
 import locale
@@ -121,7 +122,10 @@ def WriteXmlIfChanged(content, path, encoding="utf-8", pretty=False, win32=False
 
     default_encoding = locale.getdefaultlocale()[1]
     if default_encoding and default_encoding.upper() != encoding.upper():
-        xml_string = xml_string.encode(encoding)
+        if sys.platform == "win32" and sys.version_info < (3, 7):
+            xml_string = xml_string.decode("cp1251").encode(encoding)
+        else:
+            xml_string = xml_string.encode(encoding)
 
     # Get the old content
     try:

lib/find-python-script.py

@@ -0,0 +1,11 @@
+import sys, codecs;
+
+if (sys.stdout.encoding != "utf-8" and sys.platform == "win32"):
+    if sys.version_info > (3, 7):
+        sys.stdout.reconfigure(encoding='utf-8')
+        print(sys.executable)
+    else:
+        sys.stdout = codecs.getwriter("utf8")(sys.stdout)
+        print(sys.executable.decode("cp1251"))
+else:
+    print(sys.executable)

lib/find-python.js

@@ -32,7 +32,7 @@ function PythonFinder (configPython, callback) {
 
 PythonFinder.prototype = {
   log: logWithPrefix(log, 'find Python'),
-  argsExecutable: ['-c', 'import sys; print(sys.executable);'],
+  argsExecutable: [path.resolve(__dirname, 'find-python-script.py')],
   argsVersion: ['-c', 'import sys; print("%s.%s.%s" % sys.version_info[:3]);'],
   semverRange: '>=3.6.0',
 
@@ -259,7 +259,7 @@ PythonFinder.prototype = {
   run: function run (exec, args, shell, callback) {
     var env = extend({}, this.env)
     env.TERM = 'dumb'
-    const opts = { env: env, shell: shell }
+    const opts = { env: env, shell: shell, encoding: 'utf8' }
 
     this.log.silly('execFile: exec = %j', exec)
     this.log.silly('execFile: args = %j', args)