Upgrade to Webpacker 6.0.

bin/webpack-dev-server

@@ -1,15 +1,18 @@
 #!/usr/bin/env ruby
 
 ENV["RAILS_ENV"] ||= ENV["RACK_ENV"] || "development"
-ENV["NODE_ENV"]  ||= ENV["NODE_ENV"] || "development"
+ENV["NODE_ENV"]  ||= "development"
 
 require "pathname"
 ENV["BUNDLE_GEMFILE"] ||= File.expand_path("../../Gemfile",
   Pathname.new(__FILE__).realpath)
 
-require "rubygems"
 require "bundler/setup"
 
 require "webpacker"
 require "webpacker/dev_server_runner"
-Webpacker::DevServerRunner.run(ARGV)
+
+APP_ROOT = File.expand_path("..", __dir__)
+Dir.chdir(APP_ROOT) do
+  Webpacker::DevServerRunner.run(ARGV)
+end