add frontend server as a non dart dep of fuchsia_tool (#24075)

packages/flutter_tools/BUILD.gn

diff --git a/packages/flutter_tools/BUILD.gn b/packages/flutter_tools/BUILD.gn
index d5df764..30ca4bb 100644
--- a/packages/flutter_tools/BUILD.gn
+++ b/packages/flutter_tools/BUILD.gn
@@ -246,9 +246,11 @@
 
   disable_analysis = true
 
+  non_dart_deps = [
+    "//third_party/flutter/frontend_server:frontend_server_tool",
+  ]
+
   deps = [
     ":flutter_tools",
   ]
-
-  # TODO(jonahwilliams): add a frontend_server as a non dart dep.
 }