The state department of administration and the trustees of the state employees’ retirement funds, jointly and severally, are hereby authorized and empowered to enter into and execute all leases, contracts and agreements, and take any and all necessary steps, required to finance and provide for the construction of a new state office building on block 108, original plat of the city of Lansing: Provided, That the state administrative board shall approve each of the foregoing acts: And provided further, That the state administrative board may direct any of the foregoing acts to be performed by the state department of administration.