Fix stime build error with gcc-14:

machines.c: In function 'ntp_set_tod':
machines.c:484:28: error: passing argument 1 of 'stime' from incompatible pointer type [-Wincompatible-pointer-types]
  484 |                 rc = stime(&tp); /* lie as bad as SysVR4 */

Upstream: https://bugs.ntp.org/show_bug.cgi?id=3981#c2

Signed-off-by: Bernd Kuhls <bernd@kuhls.net>

--- a/libntp/machines.c	2025-05-26 18:21:43 +0000
+++ a/libntp/machines.c	2025-05-26 18:21:43 +0000
@@ -478,7 +478,7 @@ 
 #endif /* HAVE_SETTIMEOFDAY */
 #ifdef HAVE_STIME
 	if (rc && (SET_TOD_STIME == tod || !tod)) {
-		long tp = tvp->tv_sec;
+		time_t tp = tvp->tv_sec;
 
 		errno = 0;
 		rc = stime(&tp); /* lie as bad as SysVR4 */