Add preprocessor directives support

I need to add class from my source to script. I get an error  CS7021: You cannot declare namespace in script code
So tried to add something like 
```
// in script
#define SCRIPT
// in source file
#if !SCRIPT 
```
etc
but these directives does not work in scripts

https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/preprocessor-directives