Convert from using env['PLATFORM'] directly to using the more flexible
and better-thought-out Hammer env.Bits() idioms:
* env['PLATFORM'] == 'win32' => env.Bit('windows')
* env['PLATFORM'] == 'posix' => env.Bit('linux')
* env['PLATFORM'] == 'darwin' => env.Bit('mac')
New idioms:
* env.Bit('posix') => really does mean "any POSIX platform"
* env.AnyBits('mac', 'linux') => specifically mac or linux, excluding
  other POSIX platforms
Where we were using compound conditionals (e.g., "env['PLATFORM'] in
('posix', 'darwin')") I tried to take my best shot at translating
the intent (i.e., "env.Bits('posix')" for something POSIX, "not
env.Bits('mac')" for something not yet ported to Mac, etc.)
Review URL: http://codereview.chromium.org/15051

Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: b96fc5dc177d311db220dc4039e74a9c0d871558
diff --git a/zlib.scons b/zlib.scons
index d37fafa..23809d4 100644
--- a/zlib.scons
+++ b/zlib.scons
@@ -18,7 +18,7 @@
     ZLIB_LIB = ['zlib'],
 )
 
-if env['PLATFORM'] == 'win32':
+if env.Bit('windows'):
   env.Append(
       CCFLAGS = [
           '/TC',