Fix passing the --reset-cache CLI argument to Metro

Summary:
@public

While debugging a RN 0.57 blocking issue, we found that the `--reset-cache` cli arg is not being passed to Metro (more info: facebook/react-native#20567 (comment)).

This diff fixes this issue

Reviewed By: mjesun

Differential Revision: D9295634

fbshipit-source-id: a53ec7abff2b7e684a1fd88c3b53ff0b54a1c3c4

server/runServer.js

@@ -57,6 +57,7 @@ async function runServer(args: Args, config: ConfigT) {
   config.maxWorkers = args.maxWorkers;
   config.server.port = args.port;
   config.reporter = reporter;
+  config.resetCache = args.resetCache;
   config.server.enhanceMiddleware = middleware =>
     middlewareManager.getConnectInstance().use(middleware);