.github/workflows: Add docker build check (#8345)

Fixes #8344

Signed-off-by: Claire Wang <claire@tailscale.com>

.github/workflows/docker-file-build.yml

@@ -0,0 +1,15 @@
+name: "Dockerfile build"
+on: 
+  push:
+    branches:
+    - main
+  pull_request:
+    branches:
+      - "*"
+jobs:
+  deploy:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v1
+    - name: "Build Docker image"
+      run: docker build .

Dockerfile

@@ -72,4 +72,4 @@ RUN apk add --no-cache ca-certificates iptables iproute2 ip6tables
 COPY --from=build-env /go/bin/* /usr/local/bin/
 # For compat with the previous run.sh, although ideally you should be
 # using build_docker.sh which sets an entrypoint for the image.
-RUN ln -s /usr/local/bin/containerboot /tailscale/run.sh
+RUN mkdir /tailscale && ln -s /usr/local/bin/containerboot /tailscale/run.sh