qmlcachegen miscompiles value type references

Consider:

import QtQuick
QtObject {
     property font f
     function doEvil(ff: font) { ff.pointSize = 22 }
     Component.onCompleted: doEvil(f)
}

f.pointSize should end up being 22, but when compiled ahead of time it will be 0. That is because the doEvil() function is called with a simple value type wrapper, not a value type reference as it should be.

We need to avoid passing and returning of value types in AOT-compiled code until this is fixed.