Fix host arch check in pnacl common script
Fix host arch check in pnacl common script

R= sehr
BUG=none
TEST=pnacl toolchain bot

Review URL: https://chromiumcodereview.appspot.com/9855025

git-svn-id: 721b910a23eff8a86f00c8fd261a7587cddf18f8@8109 fcba33aa-ac0c-11dd-b9e7-8d5594d729c2

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