ci: validate building as ESP-IDF component

.github/workflows/push.yml

@@ -56,3 +56,36 @@ jobs:
         python-version: '3.x'
     - name: Build Sketches
       run: bash ./.github/scripts/on-push.sh 1 1 #equal and non-zero to trigger PIO
+
+  build-esp-idf-component:
+    name: Build with ESP-IDF ${{ matrix.idf_ver }} for ${{ matrix.idf_target }}
+    runs-on: ubuntu-20.04
+    strategy:
+      matrix:
+        # The version names here correspond to the versions of espressif/idf Docker image.
+        # See https://hub.docker.com/r/espressif/idf/tags and
+        # https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-guides/tools/idf-docker-image.html
+        # for details.
+        idf_ver: ["release-v4.4"]
+        idf_target: ["esp32", "esp32s2", "esp32c3"]
+    container: espressif/idf:${{ matrix.idf_ver }}
+    steps:
+      - name: Create test project
+        env:
+          IDF_TARGET: ${{ matrix.idf_target }}
+        shell: bash
+        run: |
+          . ${IDF_PATH}/export.sh
+          idf.py create-project --path $PWD test
+      - name: Check out arduino-esp32 as a component
+        uses: actions/checkout@v1
+        with:
+          submodules: recursive
+          path: components/arduino-esp32
+      - name: Build
+        env:
+          IDF_TARGET: ${{ matrix.idf_target }}
+        shell: bash
+        run: |
+          . ${IDF_PATH}/export.sh
+          idf.py build