The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/ce75ed6756a7bd8f36f252c4d8b6bdeae83b148f

commit ce75ed6756a7bd8f36f252c4d8b6bdeae83b148f
Author: Simon Glass <sjg@chromium.org>
Date: Sat Oct 07 04:31:09 2017

cros-unibuild: Fix warnings when no BSP directory is found

Don't try to find files if there is no directory. This means we don't see
an error if someone omits the directory in the unibuild case, but they
will hopefully figure it out when they see no config files installed.

Also drop the unused config variable.

BUG= chromium:772295 
TEST=manual
$ touch ~/trunk/src/third_party/chromiumos-overlay/chromeos-base/\
chromeos-firmware-null/chromeos-firmware-null-*
$ emerge-amd64-generic chromeos-firmware-null --nodeps

See that there are no more messages of the form:
find: `/mnt/host/source/src/third_party/chromiumos-overlay/chromeos-base/\
chromeos-firmware-null/../chromeos-config-bsp/files': No such file or directory

$ emerge-coral chromeos-config-bsp chromeos-config
See that it shows:
 * Installing private-model.dtsi to /usr/share/chromeos-config/dts

Change-Id: I6a961e41c2f8320926b8c82e2187997e90707a83
Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/705924
Reviewed-by: Mike Frysinger <vapier@chromium.org>

[modify] https://crrev.com/ce75ed6756a7bd8f36f252c4d8b6bdeae83b148f/eclass/cros-unibuild.eclass