Windows builds no longer needs vcvars set.
Windows builds no longer needs vcvars set.

This means windows developers can freely switch between
platform=x86-32 and platform=x86-64 in the same shell.

BUG= http://code.google.com/p/nativeclient/issues/detail?id=1551
TEST= scons platform=XXX on windows w/o vcvars set.

Review URL: http://codereview.chromium.org/6740024

git-svn-id: 721b910a23eff8a86f00c8fd261a7587cddf18f8@4697 fcba33aa-ac0c-11dd-b9e7-8d5594d729c2

sbc100/native_client,nacl-webkit/native_client,nacl-webkit/native_client,sbc100/native_client,nacl-webkit/native_client,nacl-webkit/native_client,sbc100/native_client,sbc100/native_client,nacl-webkit/native_client,sbc100/native_client,sbc100/native_client