Provide clearer message about launcher delegation (#373)

Summary:
To make it more obvious how to disable this if unwanted (e.g. when
testing local builds).
Pull Request resolved: https://github.com/facebook/flipper/pull/373

Reviewed By: jknoxville

Differential Revision: D14130771

Pulled By: passy

fbshipit-source-id: 82c83c1ad14737c8c7791de71a1ee23fcea5ec18

static/setup.js

@@ -35,6 +35,9 @@ const startLauncher = () => {
 module.exports = function(argv) {
   if (argv.launcher && isProduction() && isLauncherInstalled()) {
     console.warn('Delegating to Flipper Launcher ...');
+    console.warn(
+      `You can disable this behavior by passing '--no-launcher' at startup.`,
+    );
     startLauncher();
     process.exit(0);
   }