passt: Add clock_gettime to list of allowed syscalls

...depending on the system clock source, glibc might use it to
fetch the wall time.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

passt.c

@@ -277,6 +277,7 @@ static void pid_file(struct ctx *c) {
  * #syscalls prlimit64 epoll_ctl epoll_create1 epoll_wait accept4 accept listen
  * #syscalls socket bind connect getsockopt setsockopt recvfrom sendto shutdown
  * #syscalls openat fstat fcntl lseek clone setsid exit_group getpid
+ * #syscalls clock_gettime
  * #syscalls:pasta rt_sigreturn
  */
 int main(int argc, char **argv)