[rubygems/rubygems] Remove unnecessary `path` local variable

We can use `__dir__` directly.

https://github.com/rubygems/rubygems/commit/0e6083ca94

lib/bundler/installer/standalone.rb

@@ -14,10 +14,9 @@ module Bundler
         file.puts "require 'rbconfig'"
         file.puts "ruby_engine = RUBY_ENGINE"
         file.puts "ruby_version = RbConfig::CONFIG[\"ruby_version\"]"
-        file.puts "path = File.expand_path('..', __FILE__)"
         file.puts reverse_rubygems_kernel_mixin
         paths.each do |path|
-          file.puts %($:.unshift File.expand_path("\#{path}/#{path}"))
+          file.puts %($:.unshift File.expand_path("\#{__dir__}/#{path}"))
         end
       end
     end

spec/bundler/install/gems/standalone_spec.rb

@@ -159,7 +159,7 @@ RSpec.shared_examples "bundle install --standalone" do
     it "generates a bundle/bundler/setup.rb with the proper paths" do
       expected_path = bundled_app("bundle/bundler/setup.rb")
       extension_line = File.read(expected_path).each_line.find {|line| line.include? "/extensions/" }.strip
-      expect(extension_line).to start_with '$:.unshift File.expand_path("#{path}/../#{ruby_engine}/#{ruby_version}/extensions/'
+      expect(extension_line).to start_with '$:.unshift File.expand_path("#{__dir__}/../#{ruby_engine}/#{ruby_version}/extensions/'
       expect(extension_line).to end_with '/very_simple_binary-1.0")'
     end
   end