Fix github actions docker builds (#152)

- Use QEMU for multiplatforms (needed after updating buildx-action)
- Cleanup Dockerfile

.github/workflows/build.yml

@@ -1,5 +1,8 @@
 name: Docker builds
 
+env:
+  TARGET_PLATFORMS: linux/amd64,linux/arm/v6,linux/arm/v7,linux/arm64
+
 on:
   schedule:
     - cron: "0 10 * * *" # everyday at 10am
@@ -27,12 +30,20 @@ jobs:
           restore-keys: |
             ${{ runner.os }}-buildx-
 
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v1
+        with:
+          platforms: ${{ env.TARGET_PLATFORMS }}
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v1
+
       - name: Prepare
         id: prepare
         run: |
           DOCKER_USERNAME=viktorstrate
           DOCKER_IMAGE=viktorstrate/photoview
-          DOCKER_PLATFORMS=linux/amd64,linux/arm/v6,linux/arm/v7,linux/arm64
+          DOCKER_PLATFORMS=${TARGET_PLATFORMS}
           VERSION=edge
 
           if [[ $GITHUB_REF == refs/tags/* ]]; then
@@ -53,6 +64,7 @@ jobs:
           echo ::set-output name=docker_image::${DOCKER_IMAGE}
           echo ::set-output name=version::${VERSION}
           echo ::set-output name=buildx_args::--platform ${DOCKER_PLATFORMS} \
+            --progress=plain \
             --cache-from "type=local,src=/tmp/.buildx-cache" \
             --cache-to "type=local,dest=/tmp/.buildx-cache" \
             --build-arg VERSION=${VERSION} \
@@ -60,10 +72,7 @@ jobs:
             --build-arg VCS_REF=${GITHUB_SHA::8} \
             ${TAGS} --file Dockerfile .
 
-      - name: Set up Docker Buildx
-        uses: docker/setup-buildx-action@v1
-
-      - name: Docker Buildx (build)
+      - name: Build Docker images
         run: |
           docker buildx build --output "type=image,push=false" ${{ steps.prepare.outputs.buildx_args }}
 
@@ -74,7 +83,7 @@ jobs:
         run: |
           echo "${DOCKER_PASSWORD}" | docker login --username "${{ steps.prepare.outputs.docker_username }}" --password-stdin
 
-      - name: Docker Buildx (push)
+      - name: Push to Docker Hub
         if: success() && github.event_name != 'pull_request' && github.repository == 'viktorstrate/photoview'
         run: |
           docker buildx build --output "type=image,push=true" ${{ steps.prepare.outputs.buildx_args }}