The option {recursive,boolean()} can now be set pr directory in
'src_dirs' and 'extra_src_dirs', and on top level in the new
'erlc_compiler' option. Example config:
{erlc_compiler,[{recursive,false}]}.
{src_dirs,[{"src",[{recursive,true}]}]}.
This will cause recursive compilation within the "src" directory, but
not in any other directoires.