Perform an action after CodeReloader finishes Rebuilding

I need to run a mix task after every time Phoenix 's CodeReloader runs. The following is the single line of code I need to hook up.

   System.cmd("mix", ["custom_command"])

What I’m looking for is a hook interface for me to plug in my code.

I’ve tried creating

defmodule Mix.Tasks.Compile.Mycompiler do
  use Mix.Task.Compiler
  def run(args) do 

and passing configuring my endpoint like this:

config :my_app, MyApp.Endpoint,
    code_reloader: true,
    reloadable_compilers: Mix.compilers() ++ [:mycompiler]

But it only get’s run twice, once with this args:

args #=> ["--no-halt"]

And a second one with these:

["--purge-consolidation-path-if-stale", "<...>/_build/dev/consolidated", "--no-all-warnings"]

Any ideas how I can achieve this, using the existing CodeReloader infrastructure?