[ruby/tmpdir] Restore Ractor.yield style test for old version of Ruby

https://github.com/ruby/tmpdir/commit/f12c766996

test/test_tmpdir.rb

@@ -134,18 +134,32 @@ class TestTmpdir < Test::Unit::TestCase
 
   def test_ractor
     assert_ractor(<<~'end;', require: "tmpdir")
-      port = Ractor::Port.new
+      if defined?(Ractor::Port)
-      r = Ractor.new port do |port|
+        port = Ractor::Port.new
-        Dir.mktmpdir() do |d|
+        r = Ractor.new port do |port|
-          port << d
+          Dir.mktmpdir() do |d|
-          Ractor.receive
+            port << d
+            Ractor.receive
+          end
         end
+        dir = port.receive
+        assert_file.directory? dir
+        r.send true
+        r.join
+        assert_file.not_exist? dir
+      else
+        r = Ractor.new do
+          Dir.mktmpdir() do |d|
+            Ractor.yield d
+            Ractor.receive
+          end
+        end
+        dir = r.take
+        assert_file.directory? dir
+        r.send true
+        r.take
+        assert_file.not_exist? dir
       end
-      dir = port.receive
-      assert_file.directory? dir
-      r.send true
-      r.join
-      assert_file.not_exist? dir
     end;
   end
 end