Suppress strncpy truncation warnings with GCC 8 and later.

These warnings are bogus as the code is correct so we suppress them in
the places they occur.

unix/uxnet.c

@@ -1678,7 +1678,14 @@ Socket new_unix_listener(SockAddr listenaddr, Plug plug)
 
     memset(&u, '\0', sizeof(u));
     u.su.sun_family = AF_UNIX;
+#if __GNUC__ >= 8
+#   pragma GCC diagnostic push
+#   pragma GCC diagnostic ignored "-Wstringop-truncation"
+#endif // __GNUC__ >= 8
     strncpy(u.su.sun_path, listenaddr->hostname, sizeof(u.su.sun_path)-1);
+#if __GNUC__ >= 8
+#   pragma GCC diagnostic pop
+#endif // __GNUC__ >= 8
     addr = &u;
     addrlen = sizeof(u.su);
 

unix/uxpty.c

@@ -193,10 +193,17 @@ static void setup_utmp(char *ttyname, char *location)
     memset(&utmp_entry, 0, sizeof(utmp_entry));
     utmp_entry.ut_type = USER_PROCESS;
     utmp_entry.ut_pid = getpid();
+#if __GNUC__ >= 8
+#   pragma GCC diagnostic push
+#   pragma GCC diagnostic ignored "-Wstringop-truncation"
+#endif // __GNUC__ >= 8
     strncpy(utmp_entry.ut_line, ttyname+5, lenof(utmp_entry.ut_line));
     strncpy(utmp_entry.ut_id, ttyname+8, lenof(utmp_entry.ut_id));
     strncpy(utmp_entry.ut_user, pw->pw_name, lenof(utmp_entry.ut_user));
     strncpy(utmp_entry.ut_host, location, lenof(utmp_entry.ut_host));
+#if __GNUC__ >= 8
+#   pragma GCC diagnostic pop
+#endif // __GNUC__ >= 8
     /*
      * Apparently there are some architectures where (struct
      * utmpx).ut_tv is not essentially struct timeval (e.g. Linux