Merge branch 'mg-webpack-middleware-pass-host' into 'master'

Pass the HTTP host header to webpack-dev-server

See merge request gitlab-org/gitlab!46753

lib/gitlab/webpack/dev_server_middleware.rb

@@ -19,6 +19,7 @@ module Gitlab
       # disable SSL check since any cert used here will likely be self-signed
       def rewrite_env(env)
         env["rack.ssl_verify_none"] = true
+        env["HTTP_HOST"] = @proxy_host
         env
       end