Change Native Client x86 usr include and link path to match SDK expectations

GNU multilib style uses x86_64-nacl/include and x86_64-nacl/usr/include
but the SDK expects i686-nacl/usr/include for its files. Change the driver
to use this.

This is a cherrypick/rebase of http://reviews.llvm.org/D11271
because upstream has MIPS changes that have not been picked.

BUG= https://code.google.com/p/nativeclient/issues/detail?id=4108
R=jvoung@chromium.org

Review URL: https://codereview.chromium.org/1230653005 .