build: fix build when python path contains spaces

PR-URL: https://github.com/nodejs/node/pull/4841
Reviewed-By: Benjamin Gruenbaum <inglor@gmail.com>
Reviewed-By: Roman Reiss <me@silverwind.io>
Reviewed-By: Johan Bergström <bugs@bergstroem.nu>

configure

@@ -1102,7 +1102,7 @@ def configure_intl(o):
   return  # end of configure_intl
 
 output = {
-  'variables': { 'python': sys.executable },
+  'variables': {},
   'include_dirs': [],
   'libraries': [],
   'defines': [],

node.gyp

@@ -528,7 +528,7 @@
             }]
           ],
           'action': [
-            '<(python)',
+            'python',
             'tools/js2c.py',
             '<@(_outputs)',
             '<@(_inputs)',