Check getconf to get the bittedness of the local system.

This checks the bittedness of the local system using getconf instead of "file
/sbin/init". "file" isn't on some ChromeOS roots.

BUG=
R=thakis@chromium.org
TBR=thakis

Review URL: https://codereview.chromium.org/100053008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238493 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238493