[tools] Always use '__Internal' as the native library for .NET.

This is not the final fix, but this code will be reworked extensively, and
this fix works for now to make the interpreter work.

tools/common/Target.cs

@@ -781,7 +781,7 @@ void GenerateIOSMain (StringWriter sw, Abi abi)
 				var addDllMap = true;
 #endif
 				string mono_native_lib;
-				if (app.LibMonoNativeLinkMode == AssemblyBuildTarget.StaticObject)
+				if (app.LibMonoNativeLinkMode == AssemblyBuildTarget.StaticObject || Driver.IsDotNet)
 					mono_native_lib = "__Internal";
 				else
 					mono_native_lib = app.GetLibNativeName () + ".dylib";