Build pyauto only if the architecture of python binary matches.

BUG=none
TEST=Building 32-bit pyauto on 64-bit Linux with a 32-bit sysroot works.
Review URL: http://codereview.chromium.org/660443

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@40630 0039d316-1c4b-4281-b951-d872f2087c98
3 files changed