disk_layout_util.sh: Pass -I flag to mkfs.fat

This was to be compatible with the upgrade of the portage package
sys-fs/dosfstools from 3.0.27 to 4.1.
This ignores a *possibly* wrong error message about formatting
a device which is already partitioned. See crbug.com/901479 for
more discussion.

TEST=building seems to work as before, the error we are covering
   up seems to be a problem with udev, possibly because we're
   inside chroot.

Change-Id: I4d53b05036a285eb3b54af84f1486cc3bb532cf1
Reviewed-on: https://chromium-review.googlesource.com/1323474
Commit-Ready: Nick Crews <ncrews@chromium.org>
Tested-by: Nick Crews <ncrews@chromium.org>
Reviewed-by: Benjamin Gordon <bmgordon@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
1 file changed