Yes this happens with all non-unibuild firmware builds. I introduced this when I tried to add a check for the config, realised that I couldn't (since the USE=unibuild flag is not accessible to the code that sets up SRC_URI) and left in the code that generates the error.

Will fix.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/5e667130454777165fe122d3b4a731b983a9a660

commit 5e667130454777165fe122d3b4a731b983a9a660
Author: Simon Glass <sjg@chromium.org>
Date: Fri Sep 22 00:19:52 2017

cros-unibuild: Avoid an error when master config is missing

This file is only present with unified builds. We cope with it being
missing, but not silently:

/mnt/host/source/src/private-overlays/overlay-samus-private/chromeos-base/
	chromeos-firmware-samus/../chromeos-config-bsp/files/model.dtsi:
	No such file or directory

Fix this by only including the file if it is present.

BUG= chromium:765516 
TEST=emerge-reef chromeos-firmware
See that there is no error printed

Change-Id: I7c0d14580fdcdb1e5044e2a0f2ac4b9a00773e66
Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/675810
Reviewed-by: Jason Clinton <jclinton@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>

[modify] https://crrev.com/5e667130454777165fe122d3b4a731b983a9a660/eclass/cros-unibuild.eclass

This is fixed. We still have the following error:

20:57:31: INFO: RunCommand: /b/c/cbuild/repository/chromite/bin/cros_sdk -- /usr/bin/fdtget -l /build/reef/usr/share/chromeos-config/config.dtb /chromeos/models in /b/c/cbuild/repository
20:57:33: INFO: (stderr):
Couldn't open blob from '/build/reef/usr/share/chromeos-config/config.dtb': No such file or directory

This is harmless and does not include the word 'error', so I think it is OK for now. It will be cleaned up when we move that code to use cros_config_host.