Add custom flags to compile commands ?

Created by: aventadorm

I am working with csharp_library and I want to be able to pass a custom flag to the csc compiler. I cannot hardcode it inside features/dotnoet/CsharpLibraryCompile.java (args.add) since I want a different flag value depending on the target. A way I can think of is by creating a custom argument under csharp_library and pass it the value I want the flag to have. Is there a way to do this already or can someone tell me where the list of arguments per type of build rule are in the source code ?