ci: add QEMU setup

.github/workflows/main.yml

@@ -11,6 +11,10 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v2
+
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v1
+
       - name: Prepare zero-ui
         id: prep_zero-ui
         run: |
@@ -27,6 +31,7 @@ jobs:
       - name: Set up Docker Buildx
         id: buildx
         uses: docker/setup-buildx-action@v1
+
       - name: Cache Docker layers
         uses: actions/cache@v2
         with:
@@ -38,6 +43,7 @@ jobs:
         with:
           username: ${{ secrets.DOCKER_HUB_USERNAME }}
           password: ${{ secrets.DOCKER_HUB_ACCESS_TOKEN }}
+
       - name: Build and push zero-ui
         id: docker_build_zero-ui
         uses: docker/build-push-action@v2
@@ -49,6 +55,7 @@ jobs:
           tags: ${{ steps.prep_zero-ui.outputs.tags }}
           cache-from: type=local,src=/tmp/.buildx-cache
           cache-to: type=local,dest=/tmp/.buildx-cache
+
       - name: Build and push zerotier-controller
         id: docker_build_zerotier-controller
         uses: docker/build-push-action@v2