WIP: make the distinction between 'make' and 'make install' actually useful

We kept this stupid code from hexagonit.recipe.cmmi:

                self.run('%s %s' % (make_cmd, make_options))
                self.run('%s %s %s' % (make_cmd, make_options, make_targets))

And I'd like to stop using the following hack:

make-binary =
make-options =
make-targets = make -j1 foo install
  option1
  option2

when I want to build something else that the first target.

This minimal patch solves the above case:

_options =
  option1
  option2
make-options = foo ${:_options}
make-install-options = install ${:_options}

But not "different make-binary", and maybe we also want something more convenient. For example 6 options:

• build-binary, build-options, build-targets
• install-binary (defaults to build-binary), install-options (defaults to build-options), install-targets

/cc @vpelletier @kazuhiko @rafael