[Android]: Replace calls to getdtablesize with sysconf(_SC_OPEN_MAX) in tools.

tools/android/adb_reboot/adb_reboot.c

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <time.h>
 #include <unistd.h>
 
 int main(int argc, char ** argv) {
   int i = fork();
   struct stat ft;
   time_t ct;
 
   if (i < 0) {
     printf("fork error");
     return 1;
   }
   if (i > 0)
     return 0;
 
   /* child (daemon) continues */
   int j;
-  for (j = 0; j < getdtablesize(); j++)
+  for (j = 0; j < sysconf(_SC_OPEN_MAX); j++)
     close(j);
 
   setsid(); /* obtain a new process group */
 
   while (1) {
     sleep(120);
 
     stat("/sdcard/host_heartbeat", &ft);
     time(&ct);
     if (ct - ft.st_mtime  > 120) {
       /* File was not touched for some time. */
       system("su -c reboot");
     }
   }
 
   return 0;
 }