Sections 81-145 to 81-162 and 81-1118 to 81-1118.03 shall not apply:

(1) To the erection, construction, or original equipment of any building or addition thereto, to the construction of any road or bridge, or to the performance of any like work;

(2) To the purchase or use of the products of the labor of the inmates of any charitable, reformatory, or penal institution of the state, but section 83-146 shall apply to such products; or

(3) To the leasing by the state or a using agency of real property.