[rubygems/rubygems] Fix installing from source when same bundler vers…

…ion already a default gem

rubygems/rubygems@620119308e

lib/rubygems/commands/setup_command.rb

@@ -373,12 +373,12 @@ def install_default_bundler_gem(bin_dir)
       target_specs_dir
     end
 
-    bundler_spec = Dir.chdir("bundler") { Gem::Specification.load("bundler.gemspec") }
-    full_name = bundler_spec.full_name
+    new_bundler_spec = Dir.chdir("bundler") { Gem::Specification.load("bundler.gemspec") }
+    full_name = new_bundler_spec.full_name
     gemspec_path = "#{full_name}.gemspec"
 
     default_spec_path = File.join(specs_dir, gemspec_path)
-    Gem.write_binary(default_spec_path, bundler_spec.to_ruby)
+    Gem.write_binary(default_spec_path, new_bundler_spec.to_ruby)
 
     bundler_spec = Gem::Specification.load(default_spec_path)
 
@@ -395,16 +395,16 @@ def install_default_bundler_gem(bin_dir)
         each {|default_gem| rm_r File.join(bundler_spec.gems_dir, default_gem) }
     end
 
-    bundler_bin_dir = bundler_spec.bin_dir
+    bundler_bin_dir = new_bundler_spec.bin_dir
     mkdir_p bundler_bin_dir, mode: 0o755
     bundler_spec.executables.each do |e|
-      cp File.join("bundler", bundler_spec.bindir, e), File.join(bundler_bin_dir, e)
+      cp File.join("bundler", new_bundler_spec.bindir, e), File.join(bundler_bin_dir, e)
     end
 
     require_relative "../installer"
 
     Dir.chdir("bundler") do
-      built_gem = Gem::Package.build(bundler_spec)
+      built_gem = Gem::Package.build(new_bundler_spec)
       begin
         Gem::Installer.at(
           built_gem,
@@ -421,9 +421,9 @@ def install_default_bundler_gem(bin_dir)
       end
     end
 
-    bundler_spec.executables.each {|executable| bin_file_names << target_bin_path(bin_dir, executable) }
+    new_bundler_spec.executables.each {|executable| bin_file_names << target_bin_path(bin_dir, executable) }
 
-    say "Bundler #{bundler_spec.version} installed"
+    say "Bundler #{new_bundler_spec.version} installed"
   end
 
   def make_destination_dirs