Initial multi-arch image commit (#86)

Adding multi-arch image support for `arm64` and `amd64`. This uses dockers new `buildx` feature, to enable further architectures more work will be required to update the `runner/Dockerfile` file to pull architecture-specific releases.

The Makefile targets really should only be used for local testing and not for release, additional work to appropriately tag the release images may need to be added but for now, I've not added that logic.

Fixes: #86 

Signed-off-by: Michael Fornaro <20387402+xUnholy@users.noreply.github.com>

.github/workflows/build-runner.yml

@@ -1,22 +1,34 @@
 on:
   push:
     branches:
-    - master
+      - master
     paths:
-    - 'runner/**'
+      - 'runner/**'
 
 jobs:
   build:
     runs-on: ubuntu-latest
     name: Build runner
     steps:
-    - name: Checkout
-      uses: actions/checkout@v2
-    - name: Build container image
-      run: make docker-build
-      working-directory: runner
-    - name: Docker Login
-      run: docker login -u summerwind -p ${{ secrets.DOCKER_ACCESS_TOKEN }}
-    - name: Push container image
-      run: make docker-push
-      working-directory: runner
+      - name: Checkout
+        uses: actions/checkout@v2
+
+      - name: Set up Docker Buildx
+        id: buildx
+        uses: crazy-max/ghaction-docker-buildx@v1
+        with:
+          buildx-version: latest
+
+      - name: Login to GitHub Docker Registry
+        run: echo "${DOCKERHUB_PASSWORD}" | docker login -u "${DOCKERHUB_USERNAME}" --password-stdin
+        env:
+          DOCKERHUB_USERNAME: summerwind
+          DOCKERHUB_PASSWORD: ${{ secrets.DOCKER_ACCESS_TOKEN }}
+
+      - name: Build Container Image
+        working-directory: runner
+        run: |
+          docker buildx build \
+            --platform linux/amd64,linux/arm64 \
+            --tag summerwind/actions-runner:latest \
+            -f Dockerfile . --push