ci(vllm): install make + build deps on bigger-runner

bigger-runner is a bare self-hosted runner used by backend.yml for
docker image builds — it has docker but not the usual ubuntu-latest
toolchain. The make-based test target needs make, build-essential
(cgo in 'go test'), and curl/unzip (the Makefile protoc target
downloads protoc from github releases).

protoc-gen-go and protoc-gen-go-grpc come via 'go install' in the
install-go-tools target, which setup-go makes possible.

.github/workflows/test-extra.yml

@@ -516,6 +516,14 @@ jobs:
         uses: actions/checkout@v6
         with:
           submodules: true
+      - name: Dependencies
+        # bigger-runner is a bare self-hosted runner — install the tools
+        # we need for docker-build + protogen-go + go test (make, curl,
+        # unzip for the protoc download, build-essential for cgo).
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y --no-install-recommends \
+              make build-essential curl unzip ca-certificates git tar
       - name: Setup Go
         uses: actions/setup-go@v5
         with: