[Materials exempt from attachment or execution for

purchaser's debts.] Whenever materials shall have been furnished for use in the construction, alteration or repair of any building or other improvement, such materials shall not be subject to attachment, execution or other legal process, to enforce any debt due by the purchaser of such materials, except a debt due for the purchase-money thereof, so long as in good faith the same are about to be applied to the construction, alteration or repair of such building, mining claim or other improvement.