Ignore compilation warnings for undefined module :eldap

mix.exs

@@ -9,6 +9,7 @@ defmodule Pleroma.Mixfile do
       elixirc_paths: elixirc_paths(Mix.env()),
       compilers: [:phoenix, :gettext] ++ Mix.compilers(),
       elixirc_options: [warnings_as_errors: true],
+      xref: [exclude: [:eldap]],
       start_permanent: Mix.env() == :prod,
       aliases: aliases(),
       deps: deps(),