Skip tests with JRuby platform

Author: hsbt

tests/json_generator_test.rb

@@ -232,7 +232,7 @@ def test_buffer_initial_length
   end
 
   def test_gc
-    if respond_to?(:assert_in_out_err)
+    if respond_to?(:assert_in_out_err) && !(RUBY_PLATFORM =~ /java/)
       assert_in_out_err(%w[-rjson --disable-gems], <<-EOS, [], [])
         bignum_too_long_to_embed_as_string = 1234567890123456789012345
         expect = bignum_too_long_to_embed_as_string.to_s