MAKE: respect LIBDIR variable
MAKE: respect LIBDIR variable

Some distributions do not use plain "lib", rather "lib64"
and "lib32". Allow to control this variable.

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