legacy_apps: Add west support

Use west to fetch open-amp and libmetal library source code.

Signed-off-by: Tanmay Shah <[email protected]>

examples/legacy_apps/README.md

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+# Zephyr Example Application
+
+This repository contains legacy applications and tests examples.
+
+
+## build legacy application
+
+
+### Initialization
+
+The first step is to initialize the workspace folder (``my-workspace``) where
+the examples and all Zephyr modules will be cloned. You can do
+that by running:
+
+```shell
+# initialize my-workspace for the example-application (main branch)
+west init -m https://github.com/OpenAMP/openamp-system-reference/examples/legacy_apps/ --mr main my-workspace
+# update modules
+cd my-workspace
+west update
+```
+
+### Build and run on a board
+
+The application can be built by running:
+
+```shell
+west build -b $BOARD `$ZEPHYR_EXAMPLE`
+```
+
+where `$BOARD` is the target board and `$ZEPHYR_EXAMPLE`.
+Note that Zephyr sample boards may be used if an appropriate overlay is provided (see `app/boards`).
+
+A sample debug configuration is also provided. You can apply it by running:
+
+```shell
+west build -b $BOARD $ZEPHYR_EXAMPLE -- -DOVERLAY_CONFIG=debug.conf
+```
+
+Example to compile rpmsg_multi_services on stm32mp157 discovery board:
+
+```shell
+west build -b stm32mp157c_dk2 openamp-system-reference/examples/zephyr/rpmsg_multi_services
+```
+
+### Running on a board
+
+We consider here board on which the Zephyr image is running on a coprocessor.
+
+1) Once you have built the application copy it on target filesystem.
+2) Load the Zephyr firmware and start the coprocessor depending on the board.
+
+Example of a Zephyr firmware image loading by the Linux kernel remoteproc framework.
+
+```shell
+cp $ZEPHYR_EXAMPLE.elf /lib/modules/
+echo $ZEPHYR_EXAMPLE.elf > /sys/class/remoteproc/remoteproc0/firmware
+echo start >/sys/class/remoteproc/remoteproc0/state
+```
+
+### Running in an Emulator
+
+To be described

examples/legacy_apps/west.yml

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+# Copyright (c) 2022 STMicroelectronics
+# SPDX-License-Identifier: Apache-2.0
+
+manifest:
+  remotes:
+    - name: openamp
+      url-base: https://github.com/OpenAMP
+  defaults:
+    remote: openamp
+
+  self:
+    path: openamp-system-reference
+
+  projects:
+    - name: libmetal
+      revision: main
+
+    - name: open-amp
+      revision: main