[Proposal] Add a feature building after executing a macro

[zacky1972]

Hi,

Current Pelemay builds native code by calling make from itself after generating code and Makefile by a macro. If elixir_make will support a feature building after executing a macro, Pelemay can use it.

I'd like to contribute enhancement of elixir_make.

[josevalim]

@zacky1972 if I understand correctly, do you want to call elixir_make programmatically instead of via the mix.exs file? If so, an API that does so would be welcome, we can probably have it in the ElixirMake module, but it cannot call any functions from Mix.

[zacky1972]

Exactly. I didn't understand how to achieve such a function when I implemented Pelemay, so I implemented similar functions to elixir_make in Pelemay itself.

[whatyouhide]

A PR would be more than welcome @zacky1972. Let us know if you need any guidance, otherwise what @josevalim proposed sounds good :)