possible work around buildx inability to push

.github/workflows/build+test.yml

@@ -1,4 +1,4 @@
-name: Build/Test
+name: Build/Test/Push
 
 on: 
   push:
@@ -49,9 +49,15 @@ jobs:
           username: neale
           password: ${{ secrets.DOCKER_TOKEN }}
 
+      # Currently required, because buildx doesn't support auto-push from docker
+      - name: Set up builder
+        uses: docker/setup-buildx-action@v1
+        id: buildx
+
       - name: Build and push moth image
         uses: docker/build-push-action@v2
         with:
+          builder: ${{ steps.buildx.outputs.name }}
           target: moth
           file: build/package/Containerfile
           push: true
@@ -62,6 +68,7 @@ jobs:
       - name: Build and push moth-devel image
         uses: docker/build-push-action@v2
         with:
+          builder: ${{ steps.buildx.outputs.name }}
           target: moth
           file: build/package/Containerfile
           push: true