Revert "make test: avoid writing to $HOME"
Revert "make test: avoid writing to $HOME"

Our tests already avoid writing to $HOME and this change
only affects "make test" but not "make test_elixir" and
friends.

This reverts commit 3612dbf60f0128bf14675e7a3f602eb800ff21ff.

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