Custom server not working on Brunch 3

[Arcesilas]

Description

When trying to run a custom server, it is not started.

Expected behavior

The custom server should obviously be started

Actual behavior

The command has no effect.

On previous version of Brunch, the server is correctly started, as the log shows it:

With Brunch 3:

npx brunch watch --server
11:17:49 - info: app started on http://localhost:3333/

With Brunch 2:

npx brunch watch --server
[Wed Dec 25 11:59:50 2019] PHP 7.4.1 Development Server (http://localhost:8000) started
11:59:50 - info: custom server started, initializing watcher

Environment

1. Brunch: latest (just installed)
2. Node.js: 12.13.1
3. NPM: 6.12.1
4. Operating system: Linux Fecora 31
5. Code editor: Atom

Brunch config contents

  server: {
    command: "php -S localhost:8000 -t public/"
  },