erl -make suggestion

[Alexey Romanov]

One slight problem with erl -make is that you can't supply different
targets (e.g. one where TEST macro is defined and one where it isn't).
Adding ability to define targets would be hard to do in a
backwards-compatible way. So I suggest an option to pass a filename to
be used instead of Emakefile. Currently the simplest workaround seems
to be to create an Emakefile in a different directory, `cd` into it,
and run erl -make there.

Yours, Alexey Romanov