Skip Test::Unit::AutoRunner logic in ruby/ruby repository

tool/lib/core_assertions.rb

@@ -248,8 +248,11 @@ module Test
         at_exit {
           out.puts "#{token}<error>", [Marshal.dump($!)].pack('m'), "#{token}</error>", "#{token}assertions=#{self._assertions}"
         }
-        Test::Unit::Runner.class_variable_set(:@@stop_auto_run, true) if defined?(Test::Unit::Runner)
-        Test::Unit::AutoRunner.need_auto_run = false if defined?(Test::Unit::AutoRunner)
+        if defined?(Test::Unit::Runner)
+          Test::Unit::Runner.class_variable_set(:@@stop_auto_run, true)
+        elsif defined?(Test::Unit::AutoRunner)
+          Test::Unit::AutoRunner.need_auto_run = false
+        end
       end
 
       def assert_separately(args, file = nil, line = nil, src, ignore_stderr: nil, **opt)