Blacklist dist/ from devserver

Summary:
Having previously run `yarn build` can otherwise
cause your devserver to stop working.

Caveat: If you have a Flipper checkout and it's called neither `sonar` nor `flipper`, you're still screwed.

Reviewed By: danielbuechele

Differential Revision: D14364984

fbshipit-source-id: 1652c94a95b1dcb6d34bb9040a9cd4cd70c6df55

scripts/start-dev-server.js

@@ -63,6 +63,9 @@ function startMetroServer(app) {
         'index.js',
       ),
     },
+    resolver: {
+      blacklistRE: /\/(sonar|flipper)\/dist\//,
+    },
     watch: true,
   }).then(metroBundlerServer => {
     app.use(metroBundlerServer.processRequest.bind(metroBundlerServer));