Leases of all space in entire, free-standing buildings shall include an option to purchase exercisable by the State, unless the purchasing officer determines that inclusion of such purchase option is not in the State’s best interest and makes that determination in writing along with the reasons for making that determination and publishes the written determination in the appropriate volume of the Illinois Procurement Bulletin. Leases from governmental units and not-for-profit entities are exempt from the requirements of this Section.