Add a note that Erlang has to be installed before compiling from source
Add a note that Erlang has to be installed before compiling from source

Closes #8877

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