Changing base class based on compilation flags

build.hxml

-main Main
-swf test.swf

#here we are selecting class to extend
-D custom_base=flash.display.Bitmap

Builder.hx

import haxe.macro.Context;
import haxe.macro.Type;

class Builder{

    macro static public function getSpriteClass () : Type {
        var cls : String = (
            Context.defined("custom_base")
                ? Context.definedValue("custom_base")
                : "flash.display.Sprite" //by default use this class
        );

        return Context.getType(cls);
    }
}

Main.hx

class Main extends haxe.macro.MacroType<[Builder.getBaseClass()]> {

//some code

}