Use relative path/dir msbuild variables to map $(InputDir) and $(InputPath)

pylib/gyp/generator/msvs.py

 # Copyright (c) 2012 Google Inc. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import copy
 import ntpath
 import os
 import posixpath
 import re
 import subprocess
@@ skipping 266 matching lines @@
   platform_name = _ConfigPlatform(config_data)
   return '%s|%s' % (_ConfigBaseName(config_name, platform_name), platform_name)
 
 
 def _BuildCommandLineForRuleRaw(spec, cmd, cygwin_shell, has_input_path,
                                 quote_cmd, do_setup_env):
 
   if [x for x in cmd if '$(InputDir)' in x]:
     input_dir_preamble = (
       'set INPUTDIR=$(InputDir)\n'
-      'set INPUTDIR=%INPUTDIR:$(ProjectDir)=%\n'
+      'if NOT DEFINED INPUTDIR set INPUTDIR=.\\\n'
       'set INPUTDIR=%INPUTDIR:~0,-1%\n'
       )
   else:
     input_dir_preamble = ''
 
   if cygwin_shell:
     # Find path to cygwin.
     cygwin_dir = _FixPath(spec.get('msvs_cygwin_dirs', ['.'])[0])
     # Prepare command.
     direct_cmd = cmd
@@ skipping 3012 matching lines @@
   action_spec.extend(
       # TODO(jeanluc) 'Document' for all or just if as_sources?
       [['FileType', 'Document'],
        ['Command', command],
        ['Message', description],
        ['Outputs', outputs]
       ])
   if additional_inputs:
     action_spec.append(['AdditionalInputs', additional_inputs])
   actions_spec.append(action_spec)