Fix wrong `mrb_bug` use found with mruby-clang-plugin.
Fix build_config.rb for ArduinoDue
Merge pull request #2030 from kyab/fix-build_config-arduinodue

Fix build_config.rb for ArduinoDue
Merge pull request #2029 from take-cheeze/mrb_bug_fix

Fix wrong `mrb_bug` use found with mruby-clang-plugin.