[rubygems/rubygems] Make `gem exec` use the standard GEM_HOME

https://github.com/rubygems/rubygems/commit/032b3c518a

lib/rubygems/commands/exec_command.rb

@@ -143,7 +143,7 @@ to the same gem path as user-installed gems.
   end
 
   def set_gem_exec_install_paths
-    home = File.join(Gem.dir, "gem_exec")
+    home = Gem.dir
 
     ENV["GEM_PATH"] = ([home] + Gem.path).join(File::PATH_SEPARATOR)
     ENV["GEM_HOME"] = home

test/rubygems/test_gem_commands_exec_command.rb

@@ -749,7 +749,7 @@ class TestGemCommandsExecCommand < Gem::TestCase
       assert_match(/\A\s*\** LOCAL GEMS \**\s*\z/m, @ui.output)
 
       invoke "gem", "env", "GEM_HOME"
-      assert_equal "#{@gem_home}/gem_exec\n", @ui.output
+      assert_equal "#{@gem_home}\n", @ui.output
     end
   end