Skip loading gem version of pathname on Ruby 4.0+

Ruby 4.0 makes Pathname a built-in class, and Ruby 4.1 will make all
methods including find, rmtree, and mktmpdir built-in as well. On Ruby
4.0, only the three additional methods are redefined from the gem. On
Ruby 4.1+, the gem returns immediately and defers entirely to the
built-in implementation.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: hsbt

lib/pathname.rb

@@ -10,28 +10,14 @@
 # For documentation, see class Pathname.
 #
 
-if defined?(::Pathname) # Clear builtin Pathname
-  # :stopdoc:
-  class ::Object
-    remove_const :Pathname
-  end
+return if RUBY_VERSION >= '4.1'
 
-  # Remove module_function Pathname
-  class << ::Kernel
-    undef Pathname
-  end
-  module ::Kernel
-    undef Pathname
-  end
+unless RUBY_VERSION >= '4'
+  require 'pathname.so' if RUBY_ENGINE == 'ruby'
 
-  $".delete('pathname.so')
-  # :startdoc:
+  require_relative 'pathname_builtin'
 end
 
-require 'pathname.so' if RUBY_ENGINE == 'ruby'
-
-require_relative 'pathname_builtin'
-
 class Pathname    # * Find *
   #
   # Iterates over the directory tree in a depth first manner, yielding a