tstest/linuxdeps: add test to reject gvisor.dev/gvisor/pkg/hostarch

Updates #TODO

Signed-off-by: James Tucker <james@tailscale.com>

tstest/linuxdeps/linuxdeps.go

@@ -0,0 +1,5 @@
+package linuxdeps
+
+import (
+	_ "tailscale.com/util/linuxfw"
+)

tstest/linuxdeps/linuxdeps_test.go

@@ -0,0 +1,30 @@
+package linuxdeps
+
+import (
+	"encoding/json"
+	"os"
+	"os/exec"
+	"testing"
+)
+
+func TestDeps(t *testing.T) {
+	cmd := exec.Command("go", "list", "-json", ".")
+	cmd.Env = append(os.Environ(), "GOOS=linux", "GOARCH=arm64")
+	out, err := cmd.Output()
+	if err != nil {
+		t.Fatal(err)
+	}
+	var res struct {
+		Deps []string
+	}
+	if err := json.Unmarshal(out, &res); err != nil {
+		t.Fatal(err)
+	}
+	for _, dep := range res.Deps {
+		switch dep {
+		case "gvisor.dev/gvisor/pkg/hostarch":
+			t.Errorf("package %q is not allowed as a dependency on Linux (due to lack of support for >4K pages)", dep)
+		}
+	}
+	t.Logf("got %d dependencies", len(res.Deps))
+}