Update build-image.yaml

Author: eksrha

.github/workflows/build-image.yaml

@@ -45,7 +45,7 @@ jobs:
       - name: Set up QEMU
         uses: docker/setup-qemu-action@v1
         with:
-          platforms: $PLATFORMS
+          platforms: ${PLATFORMS}
       - name: Set up Docker Buildx
         id: buildx
         uses: docker/setup-buildx-action@v1
@@ -55,7 +55,7 @@ jobs:
         with:
           builder: ${{ steps.buildx.outputs.name }}
           context: ./docker-image/
-          platforms: $PLATFORMS
+          platforms: ${PLATFORMS}
           push: true
           tags: |
             ghcr.io/${GITHUB_REPOSITORY}:latest