Enforce VS2008.

Only to be used to drover in the relevant branches.

R=kerz@chromium.org
BUG=
TEST=To be reverted right away.

Review URL: https://chromiumcodereview.appspot.com/10387072

git-svn-id: http://src.chromium.org/svn/trunk/src/build@136545 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

gyp_chromium

@@ -107,6 +107,8 @@ if __name__ == '__main__':
     psyco.profile()
     print "Enabled Psyco JIT."
 
+  os.environ['GYP_MSVS_VERSION'] = '2008'
+
   # Fall back on hermetic python if we happen to get run under cygwin.
   # TODO(bradnelson): take this out once this issue is fixed:
   #    http://code.google.com/p/gyp/issues/detail?id=177