Set target_arch to ia32 x86_64 on 32bit userland 64bit kernel systems, scons.
Set target_arch to ia32 x86_64 on 32bit userland 64bit kernel systems, scons.

This is the scons port of https://codereview.chromium.org/342493002/

BUG=chromium:368384
R=bradnelson@google.com

Review URL: https://codereview.chromium.org/343163003

git-svn-id: 721b910a23eff8a86f00c8fd261a7587cddf18f8@13382 fcba33aa-ac0c-11dd-b9e7-8d5594d729c2

sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client