Update mix's mix.exs to fix escript.build
Update mix's mix.exs to fix escript.build

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