add_filter( 'woocommerce_attribute', 'make_product_atts_linkable', 10, 3 );
function make_product_atts_linkable( $text, $attribute, $values ) {
    $new_values = array();
    foreach ( $values as $value ) {
        if ( $attribute['is_taxonomy'] ) {

            $url = "http://link.com/" . $value;
            if ( ! empty( $url ) ) {
                $val = '<a href="' . esc_url( $url ) . '" title="' . esc_attr( $value ) . '">' . $value . '</a>';
                array_push( $new_values, $val );
            } else {
                array_push( $new_values, $value );
            }
        }
    }
    $text = implode( ', ', $new_values );
    return $text;
}