Convert from using env['PLATFORM'] directly to using the more flexible...

build/debug.scons

 # Copyright (c) 2006-2008 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.
 
 __doc__ = """
 Debug settings for Chromium builds.
 
 Incorporates "essential" and "chromium_build" settings.
 """
 
 Import("env")
 
 env.ApplySConscript([
     'internal/essential.scons',
     'internal/chromium_build${CHROMIUM_BUILD}.scons',
 ])
 
 env.Append(
     CPPDEFINES = [
         '_DEBUG',
     ],
 )
 
-if env['PLATFORM'] == 'win32':
+if env.Bit('windows'):
   if env.get('INCREMENTAL') is None:
     # INCREMENTAL was not specified on the command line or in the
     # external environment; debug default is incremental link.
     env['INCREMENTAL'] = True
     env['CHROMIUM_INCREMENTAL_FLAGS'] = '/INCREMENTAL'
 
   env.Append(
       CCFLAGS = [
           '/Od',              # VCCLCompilerTool.Optimization="0"
           '/RTC1',            # VCCLCompilerTool.BasicRuntimeChecks="3"
           '/MTd',             # VCCLCompilerTool.RuntimeLibrary="1"
       ],
       LINKFLAGS = [
           '/DEBUG',
       ],
   )