actions: add footprint diff action

This action will run on each PR and will post a comment if footprint of
some reference applications has changed, initially as a FYI but later it
will be enforced when footprint for example is gone beyond a certain
threshold.

Signed-off-by: Anas Nashif <anas.nashif@intel.com>

.github/workflows/footprint.yml

@@ -0,0 +1,69 @@
+name: Footprint Delta
+
+on: pull_request
+
+jobs:
+  footprint-cancel:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Cancel Previous Runs
+        uses: styfle/cancel-workflow-action@0.6.0
+        with:
+          access_token: ${{ github.token }}
+  footprint-delta:
+    runs-on: ubuntu-latest
+    needs: footprint-cancel
+    container:
+      image: zephyrprojectrtos/ci:v0.17.1
+      options: '--entrypoint /bin/bash'
+    strategy:
+      fail-fast: false
+    env:
+      ZEPHYR_SDK_INSTALL_DIR: /opt/toolchains/zephyr-sdk-0.12.4
+      CLANG_ROOT_DIR: /usr/lib/llvm-12
+      ZEPHYR_TOOLCHAIN_VARIANT: zephyr
+    steps:
+      - name: Cancel Previous Runs
+        uses: styfle/cancel-workflow-action@0.6.0
+        with:
+          access_token: ${{ github.token }}
+      - name: Update PATH for west
+        run: |
+          echo "$HOME/.local/bin" >> $GITHUB_PATH
+
+      - name: checkout
+        uses: actions/checkout@v2
+        with:
+          ref: ${{ github.event.pull_request.head.sha }}
+          fetch-depth: 0
+
+      - name: west setup
+        run: |
+          west init -l . || true
+          west update
+
+      - name: Detect Changes in Footprint
+        env:
+          BASE_REF: ${{ github.base_ref }}
+        run: |
+          export ZEPHYR_BASE=${PWD}
+          git config --global user.email "actions@zephyrproject.org"
+          git config --global user.name "Github Actions"
+          git remote -v
+          git rebase origin/${BASE_REF}
+          git checkout -b this_pr
+          west build -b frdm_k64f  tests/benchmarks/footprints -t ram_report
+          cp build/ram.json ram2.json
+          west build -b frdm_k64f  tests/benchmarks/footprints -t rom_report
+          cp build/rom.json rom2.json
+
+          git checkout origin/${BASE_REF}
+          west update
+          west build -p always -b frdm_k64f  tests/benchmarks/footprints -t ram_report
+          west build -b frdm_k64f  tests/benchmarks/footprints -t rom_report
+          cp build/ram.json ram1.json
+          cp build/rom.json rom1.json
+
+          git checkout this_pr
+          ./scripts/footprint/fpdiff.py ram1.json ram2.json
+          ./scripts/footprint/fpdiff.py rom1.json rom2.json