Test rpi using buildx and dockerfile.armhf

Uses piwheels for pi image

.github/workflows/ci.yml

@@ -6,6 +6,7 @@ on:
       - master
       - develop
       - github_actions_tests
+      - rpi_crosscompile
     tags:
     release:
       types: [published]
@@ -226,25 +227,37 @@ jobs:
         user: __token__
         password: ${{ secrets.pypi_password }}
 
+    - name: Dockerhub login
+      env:
+        DOCKER_PASSWORD: ${{ secrets.DOCKER_PASSWORD }}
+        DOCKER_USERNAME: ${{ secrets.DOCKER_USERNAME }}
+      run: |
+        echo "${DOCKER_PASSWORD}" | docker login --username ${DOCKER_USERNAME} --password-stdin
+
     - name: Build and test and push docker image
       env:
         IMAGE_NAME: freqtradeorg/freqtrade
-        DOCKER_USERNAME: ${{ secrets.DOCKER_USERNAME }}
-        DOCKER_PASSWORD: ${{ secrets.DOCKER_PASSWORD }}
         BRANCH_NAME: ${{ steps.extract_branch.outputs.branch }}
       run: |
         build_helpers/publish_docker.sh
 
-    - name: Build raspberry image for ${{ steps.extract_branch.outputs.branch }}_pi
-      uses: elgohr/Publish-Docker-Github-Action@2.7
+    - name: Set up Docker Buildx
+      id: buildx
+      uses: crazy-max/ghaction-docker-buildx@v1
       with:
-        name: freqtradeorg/freqtrade:${{ steps.extract_branch.outputs.branch }}_pi
-        username: ${{ secrets.DOCKER_USERNAME }}
-        password: ${{ secrets.DOCKER_PASSWORD }}
-        dockerfile: Dockerfile.pi
-        # cache: true
-        cache: ${{ github.event_name != 'schedule' }}
-        tag_names: true
+        buildx-version: latest
+        qemu-version: latest
+
+    - name: Available platforms
+      run: echo ${{ steps.buildx.outputs.platforms }}
+
+    - name: Build Raspberry docker image
+      env:
+        IMAGE_NAME: freqtradeorg/freqtrade
+        BRANCH_NAME: ${{ steps.extract_branch.outputs.branch }}
+      run: |
+        build_helpers/publish_docker_pi.sh
+
 
     - name: Slack Notification
       uses: homoluctus/slatify@v1.8.0