[dce][js] Unnecessary code in "hello world" sample

After #9167 every compiled js now contains following lines (even if these functions are never used):
```js
function $iterator(o) { if( o instanceof Array ) return function() { return new haxe_iterators_ArrayIterator(o); }; return typeof(o.iterator) == 'function' ? $bind(o,o.iterator) : o.iterator; }
var $_;
function $bind(o,m) { if( m == null ) return null; if( m.__id__ == null ) m.__id__ = $global.$haxeUID++; var f; if( o.hx__closures__ == null ) o.hx__closures__ = {}; else f = o.hx__closures__[m.__id__]; if( f == null ) { f = m.bind(o); o.hx__closures__[m.__id__] = f; } return f; }
$global.$haxeUID |= 0;
Main.main();
})(typeof window != "undefined" ? window : typeof global != "undefined" ? global : typeof self != "undefined" ? self : this);
```
Together with [`ArrayIterator`included in every compiled js](https://github.com/HaxeFoundation/haxe/issues/9185) it gets quite ugly for minimal samples.