workflow: Add workflow verifing integration with the upstream Zephyr

During the workflow a Zephyr repository is checked out (by default
main, but any version can be given when workflow is triggered
manually) and west update is run according to Zephyr's manifest.
However, the MCUboot version is then replaced by checking out
MCUboot main (triggered by push or cron), PR's head (triggered by
a PR to MCUboot) or custom SHA (manual trigger). Next, twister is
called for tests/builds in locations given in the workflow
(test_paths).

Signed-off-by: Maciej Perkowski <Maciej.Perkowski@nordicsemi.no>

.github/workflows/zephyr_build.yaml

@@ -0,0 +1,103 @@
+# Copyright (c) 2022 Nordic Semiconductor ASA
+# SPDX-License-Identifier: Apache-2.0
+
+name: Build Zephyr samples with Twister
+
+# Workflow triggers on PRs, pushes to main, once per day at midnight and can be started manually.
+on:
+  # By default, pull_request includes: opened, synchronize, or reopened
+  pull_request:
+    branches:
+      - main
+  push:
+    branches:
+      - main
+  schedule:
+    - cron: 0 0 * * *
+  # When triggered manually, ask for Zephyr and MCUBoot versions to check out
+  workflow_dispatch:
+    inputs:
+      version_zephyr:
+        description: 'Which Zephyr version to checkout?'
+        required: true
+        default: 'main'
+      version_mcuboot:
+        description: 'Which MCUBoot version to checkout?'
+        required: true
+        default: 'main'
+
+env:
+  ZEPHYR_VERSION: 'main'
+  MCUBOOT_VERSION: 'main'
+
+# Only cancel ongoing runs for PRs
+concurrency:
+  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
+jobs:
+  build_zephyr_with_twister:
+    runs-on: ubuntu-latest
+    # Docker image from the zephyr upstream. Includes SDK and other required tools
+    container:
+      image: zephyrprojectrtos/ci:v0.21.0
+      options: '--entrypoint /bin/bash'
+      volumes:
+        - /home/runners/zephyrproject:/github/cache/zephyrproject
+    env:
+      ZEPHYR_SDK_INSTALL_DIR: /opt/toolchains/zephyr-sdk-0.13.2
+
+    steps:
+      - name: Set versions when workflow_dispatch
+        if: github.event_name == 'workflow_dispatch'
+        run: |
+          echo "ZEPHYR_VERSION=${{ github.event.inputs.version_zephyr }}" >> $GITHUB_ENV
+          echo "MCUBOOT_VERSION=${{ github.event.inputs.version_mcuboot }}" >> $GITHUB_ENV
+
+      - name: Set versions when pull_request
+        if: github.event_name == 'pull_request'
+        run: |
+          echo "MCUBOOT_VERSION=${{ github.event.pull_request.head.sha }}" >> $GITHUB_ENV
+
+      - name: Checkout Zephyr
+        uses: actions/checkout@v2
+        with:
+          repository: 'zephyrproject-rtos/zephyr'
+          ref: ${{ env.ZEPHYR_VERSION }}
+          path: 'repos/zephyr'
+
+      - name: Setup Zephyr
+        working-directory: repos/zephyr
+        run: |
+          west init -l .
+          west update
+
+      - name: Checkout MCUBoot
+        uses: actions/checkout@v2
+        with:
+          repository: 'mcu-tools/mcuboot'
+          ref: ${{ env.MCUBOOT_VERSION }}
+          path: 'repos/bootloader/mcuboot'
+
+      - name: Run Twister tests
+        working-directory: repos/zephyr
+        env:
+          test_paths: >
+              -T ../bootloader/mcuboot/boot/zephyr
+              -T ./tests/subsys/dfu
+              -T ./samples/subsys/mgmt/mcumgr/smp_svr
+        run: |
+          export ZEPHYR_BASE=${PWD}
+          export ZEPHYR_TOOLCHAIN_VARIANT=zephyr
+          echo "Using Zephyr version: ${{ env.ZEPHYR_VERSION }}"
+          echo "Using Mcuboot version: ${{ env.MCUBOOT_VERSION }}"
+          ./scripts/twister --inline-logs -v -N -M --integration --overflow-as-errors --retry-failed 2 ${test_paths}
+
+      - name: Upload Tests Results
+        uses: actions/upload-artifact@v2
+        if: always()
+        with:
+          name: Tests Results
+          if-no-files-found: ignore
+          path: |
+            repos/zephyr/twister-out/twister.xml