If the board of county commissioners at any regular or extra meeting adopts and enters in the minutes of its proceedings a resolution declaring that it is necessary to acquire for the use of the county any land, describing it, to be used as a site for a courthouse or other public building or to enlarge the site of a courthouse or other public building already owned by the county, and the board of county commissioners is unable to purchase the land at a reasonable price, the land may be acquired by condemnation as provided in chapter 117.