dump to stdout

* test/objspace/test_objspace.rb (test_dump_all): dump to stdout
  instead of a string, get rid of hung up.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@55391 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/objspace/test_objspace.rb

@@ -308,9 +308,16 @@ class TestObjSpace < Test::Unit::TestCase
     end
 
     if defined?(JSON)
-      assert_ruby_status(%w[-rjson -robjspace], "#{<<-"begin;"}\n#{<<-"end;"}")
+      args = [
+        "-rjson", "-",
+        EnvUtil.rubybin,
+        "--disable=gems", "-robjspace", "-eObjectSpace.dump_all(output: :stdout)",
+      ]
+      assert_ruby_status(args, "#{<<~"begin;"}\n#{<<~"end;"}")
       begin;
-        JSON.parse(ObjectSpace.dump_all(output: :string))
+        IO.popen(ARGV) do |f|
+          JSON.load(f)
+        end
       end;
     end
   end