Add the ability that can use a specify compiler to compile the csharp code

After I read your code. I found that you use the csc to compile the csharp code first if it exists. But I encounter a problem that if I use the dll, which is compiled by the csc, in Unity, it would cause an "Internal compiler error". But the problem will not exists if I use the mcs compiler to compile the csharp code to dll. So I need the ability that can use a specify compiler to compile the csharp code.