Make attr_accessor benchmark compatible with ractors

Author: etiennebarrie

benchmarks.yml

@@ -139,6 +139,7 @@ attr_accessor:
   desc: attr_accessor tests the performance of getting instance variable values via an attr_accessor imemo.
   category: micro
   single_file: true
+  ractor: true
 keyword_args:
   desc: keyword_args tests the performance of method calls with keyword arguments.
   category: micro

benchmarks/attr_accessor.rb

@@ -34,8 +34,9 @@ def get_value_loop
   end
 end
 
-obj = TheClass.new
+OBJ = TheClass.new
+Ractor.make_shareable(OBJ)
 
-run_benchmark(850) do
-  obj.get_value_loop
+run_benchmark(10) do
+  OBJ.get_value_loop
 end