The script would previously attempt to run
the x86_32 version of ninja on 32-bit arches
such as mips and arm rather than display the
error message.

This error showed up an ARM builder:
/mnt/data/b/depot_tools/ninja: line 25: /mnt/data/b/depot_tools/ninja-linux32: cannot execute binary file

Review URL: https://codereview.chromium.org/26490004

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@227549 0039d316-1c4b-4281-b951-d872f2087c98