In any municipality in which there shall have been established a free public library pursuant to law, the governing body may, by resolution, accept gifts or bequests for the purpose of building a library building therein which may be made on condition that a sum not exceeding ten per cent of the amount of such gift or bequest be annually appropriated for the maintenance and support of such library, or which may be made on the above condition and on the further condition that the municipality to which such gift is made shall also provide a suitable site for the building. When any such conditional gift is accepted by any municipality such amount as may be required by the condition of the gift for the support and use of the library may be raised annually by taxation.