image: re-generate udev's hwdb.bin as part of building image

Newer udev versions do not pay attention to individual *.hwdb files
anymore, but require up-to-date /etc/udev/hwdb.bin. That means we can
no longer simply drop individual hwdb files into bsp packages and expect
them to work, we need to update hwdb.bin. Instead of wiring up the
update into individual bsp ebuilds, let's [re]generate hwdb.bin as
part of image build process.

BUG=b:36735408
TEST=Build Eve's image, check assistant key referenced in
/etc/udev/hwdb.bin

Change-Id: Idf15d2be0a8e448793a994c472178afbfbd67892
Reviewed-on: https://chromium-review.googlesource.com/553720
Commit-Ready: Dmitry Torokhov <dtor@chromium.org>
Tested-by: Dmitry Torokhov <dtor@chromium.org>
Reviewed-by: Chirantan Ekbote <chirantan@chromium.org>
2 files changed