When trying to build IronRuby for a v2Release under Mono 2.10.2, I'm
getting a failure:
 
% git clone https://github.com/IronLanguages/main.git IronLanguages
% cd IronLanguages
% xbuild Solutions/Ruby.sln /p:Configuration="v2Release"
...
Builtins/RangeOps.cs(307,17): error CS0266: Cannot implicitly convert
type System.Collections.Generic.IEnumerable<IronRuby.Builtins.MutableString>'
toSystem.Collections.Generic.IEnumerable<object>'. An explicit
conversion exists (are you missing a cast?)
 
Building for the regular configuration is fine.

            return EachStepString(storage, self, ConvertStepToInt(storage, step)).Cast<object>();

            return EachStepString(storage, self, ConvertStepToInt(storage, step));

            return EachStepString(storage, self, ConvertStepToInt(storage, step)).Cast<object>();