Document defoverridable behaviour regarding compilation callbacks
Document defoverridable behaviour regarding compilation callbacks

Closes #7340

gfvcastro/elixir,kelvinst/elixir,kelvinst/elixir,pedrosnk/elixir,gfvcastro/elixir,elixir-lang/elixir,pedrosnk/elixir,michalmuskala/elixir,kimshrier/elixir,lexmag/elixir,ggcampinho/elixir,lexmag/elixir,ggcampinho/elixir,joshprice/elixir,kimshrier/elixir