build: use GHA cache and dockerx for docker dev build

Signed-off-by: deadprogram <ron@hybridgroup.com>

.github/workflows/build-tinygo-dev-docker.yml

@@ -15,6 +15,8 @@ jobs:
         uses: actions/checkout@v2
         with:
           submodules: recursive
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v1
       - name: Docker meta
         id: meta
         uses: docker/metadata-action@v3
@@ -43,3 +45,5 @@ jobs:
           push: true
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
+          cache-from: type=gha
+          cache-to: type=gha,mode=max