feat: add arm64/linux support to Docker build workflows

Add QEMU and Buildx setup steps to both image build workflows,
and set platforms: linux/amd64,linux/arm64 for multiarch images.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.github/workflows/build-disk-collector.yml

@@ -34,6 +34,10 @@ jobs:
     steps:
       - name: Checkout code
         uses: actions/checkout@v4
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v3
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
       - name: Log in to GitHub Container Registry
         uses: docker/login-action@v2
         with:
@@ -45,6 +49,7 @@ jobs:
         with:
           context: install/sidecar-disk-collector
           push: true
+          platforms: linux/amd64,linux/arm64
           tags: |
             ghcr.io/crosstalk-solutions/project-nomad-disk-collector:${{ inputs.version }}
             ghcr.io/crosstalk-solutions/project-nomad-disk-collector:v${{ inputs.version }}

.github/workflows/build-primary-image.yml

@@ -34,6 +34,10 @@ jobs:
     steps:
       - name: Checkout code
         uses: actions/checkout@v4
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v3
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
       - name: Log in to GitHub Container Registry
         uses: docker/login-action@v2
         with:
@@ -44,6 +48,7 @@ jobs:
         uses: docker/build-push-action@v5
         with:
           push: true
+          platforms: linux/amd64,linux/arm64
           tags: |
             ghcr.io/crosstalk-solutions/project-nomad:${{ inputs.version }}
             ghcr.io/crosstalk-solutions/project-nomad:v${{ inputs.version }}