Support 32-bit EFI boot

Build and install bootia32.efi for use from 32-bit EFI BIOSes, alongside
the bootx64.efi used for 64-bit EFI BIOSes.

BUG=chrome-os-partner:18940
TEST=Built and tested a USB image on a system that only supports
     32-bit EFI boot, not 64-bit EFI boot.
CQ-DEPEND=Ib65f7effe0d09ae8690dcdfff76327e43720eed6

Change-Id: If13cd6c0529ea614c73f6b933450925fc3ca7714
Reviewed-on: https://gerrit.chromium.org/gerrit/49197
Tested-by: Josh Triplett <josh@joshtriplett.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Josh Triplett <josh@joshtriplett.org>
2 files changed