Math.cos example fails when targeting HashLink

While trying to follow the example code

```haxe
var script = "
var sum = 0;
for( a in angles )
sum += Math.cos(a);
sum;
";
var parser = new hscript.Parser();
var program = parser.parseString(script);
var interp = new hscript.Interp();
interp.variables.set("Math",Math); // share the Math class
interp.variables.set("angles",[0,1,2,3]); // set the angles list
trace( interp.execute(program) );
```

with latest haxe 4.1.2 and hashlink 1.11.0, I get the error "Invalid function null" when it tries to find the cos function in Math. This -appears- to be a hashlink bug? But I'm not entirely sure if maybe there's a way around it that should be done in hscript instead.

The code executes as expected with both js and interp.

```haxe
Reflect.getProperty(Math, "cos"); //null for HashLink target
```