chromeos-config: add firmware build target for bmpblk

Add a config option for a firmware-specific bmpblk configuration.
This will enable different models to have different resolution
firmware graphics.

BUG=b:157510689
TEST=./run_tests.sh

Change-Id: I3d35752f9ed08500a983352dc4356c5976011962
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform2/+/3060422
Tested-by: Jack Rosenthal <jrosenth@chromium.org>
Auto-Submit: Jack Rosenthal <jrosenth@chromium.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>
Reviewed-by: C Shapiro <shapiroc@chromium.org>
Commit-Queue: C Shapiro <shapiroc@chromium.org>
(cherry picked from commit 8659aa9c56e25c5b699f1bd0b4fc1e6df221b047)
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform2/+/3177860
Reviewed-by: Jack Rosenthal <jrosenth@chromium.org>
Reviewed-by: Shawn Ku <shawnku@chromium.org>
Commit-Queue: Joshua Emele <jemele@chromium.org>
Tested-by: Joshua Emele <jemele@chromium.org>
diff --git a/chromeos-config/README.md b/chromeos-config/README.md
index 5d851da..0847e53 100644
--- a/chromeos-config/README.md
+++ b/chromeos-config/README.md
@@ -527,6 +527,7 @@
 | Attribute | Type   | RegEx     | Required | Oneof Group | Build-only | Description |
 | --------- | ------ | --------- | -------- | ----------- | ---------- | ----------- |
 | base | string |  | False |  | True | Build target of the base EC firmware for a detachable device, that will be considered dirty when building/testing |
+| bmpblk | string |  | False |  | True | Build target that will be considered dirty when building/testing locally. |
 | coreboot | string |  | False |  | True | Build target that will be considered dirty when building/testing locally. |
 | depthcharge | string |  | False |  | True | Build target that will be considered dirty when building/testing locally. |
 | ec | string |  | False |  | True | Build target that will be considered dirty when building/testing locally. |
diff --git a/chromeos-config/cros_config_host/cros_config_schema.yaml b/chromeos-config/cros_config_host/cros_config_schema.yaml
index c8ae8d4..45481cd 100644
--- a/chromeos-config/cros_config_host/cros_config_schema.yaml
+++ b/chromeos-config/cros_config_host/cros_config_schema.yaml
@@ -600,6 +600,7 @@
                       items:
                         type: string
                         description: Extra EC build targets to build within chromeos-ec.
+                    bmpblk: *firmware_build_target
                     coreboot: *firmware_build_target
                     gsc: *firmware_build_target
                     depthcharge: *firmware_build_target