factor::numeric::gcd: Silence the (erroneous) dead code lint
use std::mem::swap;
-pub fn gcd(mut a: u64, mut b: u64) -> u64 {
+// This is incorrectly reported as dead code,
+// presumably when included in build.rs.
+#[allow(dead_code)]
+pub(crate) fn gcd(mut a: u64, mut b: u64) -> u64 {
while b > 0 {
a %= b;
swap(&mut a, &mut b);
