Add preliminary external config sample

This sample source code is an empty file (no symbol for main()).
All functionality is eabled through the configuration settings.

The system should successfully build this sample with the following command:

  './zephyr/scripts/twister --testsuite-root mcuboot/samples/zephyr_external_config'

Incremental verification:

1. (Pass) west build -p always -b nrf52840dk_nrf52840 mcuboot/boot/zephyr
2. (Pass) ./zephyr/scripts/twister --testsuite-root zephyr/tests/subsys/dfu
3. (Pass) ./zephyr/scripts/twister --testsuite-root zephyr/samples/subsys/mgmt/mcumgr/smp_svr/
4. (Pass) ./zephyr/scripts/twister --testsuite-root mcuboot/boot/zephyr
5. (FAIL) ./zephyr/scripts/twister --testsuite-root mcuboot/samples/zephyr_external_config

This new sample is expected to fail while we evolve the minimum
implementation to support it.

Currently the build failure message is:
'''
error: MCUBOOT (defined at Kconfig.zephyr:682) is assigned in a configuration file, but is not
directly user-configurable (has no prompt). It gets its value indirectly from other symbols. See
http://docs.zephyrproject.org/latest/kconfig.html#CONFIG_MCUBOOT and/or look up MCUBOOT in the
menuconfig/guiconfig interface. The Application Development Primer, Setting Configuration Values,
and Kconfig - Tips and Best Practices sections of the manual might be helpful too.
'''

Signed-off-by: Gregory Shue <[email protected]>

Author: legrand-gregshue

samples/zephyr_external_config/CMakeLists.txt

@@ -0,0 +1,9 @@
+# Copyright (c) 2022 Legrand North America, LLC.
+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.20.0)
+
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(mcuboot_exernal_config)
+
+target_sources(app PRIVATE empty.c)

samples/zephyr_external_config/README.rst

@@ -0,0 +1,26 @@
+.. _mcuboot_external_config:
+
+MCUBoot External Config
+#######################
+
+Overview
+********
+
+A simple sample illustrating how to configure an MCUBoot image build
+from a different module.
+
+Building and Running
+********************
+
+This application can be built and executed on QEMU as follows:
+
+.. code-block:: console
+
+  west build -b nrf52840dk_nrf52840 \
+    bootloader/mcuboot/samples/zephyr_external_config
+
+
+Sample Output
+=============
+
+None.

samples/zephyr_external_config/empty.c

@@ -0,0 +1 @@
+/* This file is intentionally empty */

samples/zephyr_external_config/prj.conf

@@ -0,0 +1,13 @@
+# Copyright (c) 2022 Legrand North America, LLC.
+# SPDX-License-Identifier: Apache-2.0
+
+CONFIG_MCUBOOT=y
+
+CONFIG_LOG=y
+CONFIG_LOG_MODE_MINIMAL=y
+CONFIG_LOG_DEFAULT_LEVEL=0
+CONFIG_CBPRINTF_NANO=y
+
+CONFIG_FLASH=y
+CONFIG_DEBUG=y
+CONFIG_PM=n

samples/zephyr_external_config/sample.yaml

@@ -0,0 +1,16 @@
+# Copyright (c) 2022 Legrand North America, LLC.
+# SPDX-License-Identifier: Apache-2.0
+
+sample:
+  description: MCUBoot external config
+  name: MCUBoot external config
+common:
+    tags: bootloader_mcuboot
+    platform_allow:  nrf52840dk_nrf52840 frdm_k64f disco_l475_iot1
+    integration_platforms:
+      - nrf52840dk_nrf52840
+      - frdm_k64f
+      - disco_l475_iot1
+tests:
+  mcuboot.sample.mcuboot_external_config:
+    tags: bootloader_mcuboot

west.yml

@@ -0,0 +1,32 @@
+# Copyright (c) 2022 Legrand North America, LLC.
+#
+# SPDX-License-Identifier: Apache-2.0
+
+# The west manifest file for Zephyr ecosystem development.
+#
+# Usage:
+# west init -m https://github.com/mcu-tools/mcuboot
+# west update
+
+manifest:
+  version: "0.12"
+
+  remotes:
+    - name: zephyrproject
+      url-base: https://github.com/zephyrproject-rtos
+    - name: mcu-tools
+      url-base: https://github.com/mcu-tools
+
+  defaults:
+    remote: mcu-tools
+
+  projects:
+    - name: zephyr
+      revision: main
+      remote: zephyrproject
+      import:
+        name-blocklist:
+          - mcuboot
+
+  self:
+    path: mcuboot