fix: Require native extension through Thermite::Fiddle

Second attempt to fix #12.

Thermite builds native extension as .so file while
Rutie loads the module as .dylib on MacOS.

ext/Rakefile

@@ -1,5 +1,10 @@
 require "thermite/tasks"
 
-project_dir = File.dirname(File.dirname(__FILE__)) # rubocop:disable Style/NestedFileDirname
-Thermite::Tasks.new(cargo_project_path: project_dir, ruby_project_path: project_dir)
+project_dir = File.expand_path("../..", __FILE__)
+
+Thermite::Tasks.new(
+  cargo_project_path: project_dir,
+  ruby_project_path: project_dir
+)
+
 task default: %w[thermite:build]

lib/tantiny.rb

@@ -4,6 +4,7 @@
 RubyNext::Language.setup_gem_load_path
 
 require "rutie"
+require "thermite/fiddle"
 require "concurrent"
 require "fileutils"
 
@@ -16,5 +17,11 @@
 require "tantiny/index"
 
 module Tantiny
-  Rutie.new(:tantiny, lib_path: __dir__, lib_prefix: "").init("Init_tantiny", __dir__)
+  project_dir = File.expand_path("../..", __FILE__)
+
+  Thermite::Fiddle.load_module(
+    "Init_tantiny",
+    cargo_project_path: project_dir,
+    ruby_project_path: project_dir
+  )
 end