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

third_party/lzma_sdk/lzma_sdk.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.
 
 Import('env')
 
 env = env.Clone()
 
 if env.WantSystemLib('lzma_sdk'):
   Return()
 
 env.Prepend(
     CPPPATH = [
         '.',
         '$CHROME_SRC_DIR',
     ]
 )
 
 env.Append(
     CPPDEFINES = [
         '_LZMA_PROB32',
         '_LZMA_IN_CB',
     ],
 )
 
-if env['PLATFORM'] == 'win32':
+if env.Bit('windows'):
   env.Append(
     CCFLAGS = [
         '/TC',
         '/wd4800',
     ],
   )
 
 input_files = [
     '7zCrc.c',
     'Archive/7z/7zAlloc.c',
     'Archive/7z/7zBuffer.c',
     'Archive/7z/7zDecode.c',
     'Archive/7z/7zExtract.c',
     'Archive/7z/7zHeader.c',
     'Archive/7z/7zIn.c',
     'Archive/7z/7zItem.c',
     'Archive/7z/7zMethodID.c',
     'Compress/Branch/BranchX86.c',
     'Compress/Branch/BranchX86_2.c',
     'Compress/Lzma/LzmaDecode.c',
 ]
 
 env.ChromeStaticLibrary('lzma_sdk', input_files)