[Rubygems-developers] does rubygems support platform-specific gem dependencies?

[Stephen Bannasch]

I've patched the highline gem to use 'ffi-ncurses' when it is running 
in jruby instead of `stty` (which doesn't work properly in jruby).

See:

   http://github.com/stepheneb/highline/tree/jruby

Is there a way to add a platform-specific gem dependency in a 
Gem::Specification?

Right now I throw an error telling users to install ff-ncurses manually.