test.hx

class Test {
    @:keep public static function main() {
        if(Reflect.hasField(Test2, "main")) {
            Reflect.callMethod(Test2, Reflect.field(Test2, "main"), []);
        }
        
        trace("Haxe is great!");
    }
}

class Test2 {
    @:keep public static function main() {
        trace("Dynamic");
    }
}