Access Ractor::Selector by calling C API without Ruby build

access_ractor_selector.rb

if true then
  # Fiddle version
  require 'fiddle'
  module Fiddle
    Function.new(dlopen(nil).sym('rb_init_ractor_selector'), [], TYPE_VOID).call
  end
else
  # FFI version
  require 'ffi'
  Module::new{
    extend FFI::Library
    ffi_lib FFI::CURRENT_PROCESS
    attach_function :rb_init_ractor_selector, [], :void
  }::rb_init_ractor_selector
end