Isolate stages from effects of earlier vcvarsall.bat calls.
Isolate stages from effects of earlier vcvarsall.bat calls.

Wrap all environment changes in setlocal/endlocal pairs.

Note: first setlocal does not have a pair. It's pair is implicit
endlocal at the end of script.
Review URL: http://codereview.chromium.org/6894002

git-svn-id: 721b910a23eff8a86f00c8fd261a7587cddf18f8@4977 fcba33aa-ac0c-11dd-b9e7-8d5594d729c2

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