Notwithstanding any other provision of law, any county having highways in the primary or secondary state highway system may contribute funds annually for the construction of primary or secondary highways. The funds contributed by such county shall be appropriated from the county’s general revenues for use by the Department on the primary or secondary state highway system within such county as may be determined by the board of supervisors of such county in cooperation with the Department. The funds to which any county may be entitled under the provisions of § 33.2-358 for construction, improvement, or maintenance of primary or secondary highways shall not be diminished by reason of any funds contributed for that purpose by such county or by any person or entity, regardless of whether such contributions are matched by state or federal funds.