It would be nice to be able to use `mkmf` without `libruby`. Motivating use-case: Many gems provide Ruby bindings to C ABI via [Ruby FFI](https://github.com/ffi/ffi) instead of libruby. This is because Ruby FFI is easier to use, is compatible with JRuby out-of-the-box, and allows binding to system libraries without compilation. I currently use the following set of hacks to stop `mkmf` from including libruby: `ext/extconf.rb`: ``` ruby # Don't link libruby. $LIBRUBYARG = nil # Disable .def file generation for mingw, as it defines an # `Init_libsass` export which we don't have. MakeMakefile.send(:remove_const, :EXPORT_PREFIX) MakeMakefile::EXPORT_PREFIX = nil ``` `ext/depend`: ``` Makefile ruby # Replaces default mkmf dependencies. Default mkmf dependencies include all libruby headers. # We don't need libruby and some of these headers are missing on JRuby (breaking compilation there). $(OBJS): $(HDRS) ``` (full example: https://github.com/sass/sassc-ruby/tree/master/ext) It'd be nice to have mkmf support for this without hacks.