Define the fork handshake byte unconditionally.

1861a881eb made the declaration of "a"
conditional on HAVE_LINUX_NETWORK, which was right as long as the
read_write() calls sat inside the same #ifdef.

Since 1da5cc2951 the parent blocks on
the pipe and the child writes the byte on every platform, so a build
without HAVE_LINUX_NETWORK now fails with "a undeclared" in both
do_tcp_connection() and swap_to_tcp(). This is easy to hit after
7ebe7ebb93, which gives *BSD a reason
to take that path.

Signed-off-by: DL6ER <dl6er@dl6er.de>

src/dnsmasq.c

@@ -2021,9 +2021,7 @@ static void do_tcp_connection(struct listener *listener, time_t now, int slot)
   struct in_addr netmask;
   int pipefd[2];
   struct iovec tcpbuff;
-#ifdef HAVE_LINUX_NETWORK
   unsigned char a = 0;
-#endif
   netmask.s_addr = 0;
   
   while ((confd = accept(listener->tcpfd, NULL, NULL)) == -1 && errno == EINTR);
@@ -2258,9 +2256,7 @@ int swap_to_tcp(struct frec *forward, time_t now, int status, struct dns_header
     {
       pid_t p;
       int i, pipefd[2];
-#ifdef HAVE_LINUX_NETWORK
       unsigned char a = 0;
-#endif
       
       /* check to see if we have a free tcp process slot. */
       for (i = daemon->max_procs - 1; i >= 0; i--)