Make --gdb explain that it doesn't work right now

sky/tools/skydb

 #!/usr/bin/env python
 # Copyright 2014 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.
 
 import skypy.paths
 from skypy.skyserver import SkyServer
 import argparse
 import json
 import logging
@@ skipping 97 matching lines @@
         ]
         # FIXME: This probably is wrong for android?
         if args.use_osmesa:
             shell_args.append('--args-for=mojo:native_viewport_service --use-osmesa')
 
         if 'remote_sky_server_port' in self.pids:
             shell_command = self._wrap_for_android(shell_args)
         else:
             shell_command = [self.paths.mojo_shell_path] + shell_args
 
-        # FIXME: This doesn't work for android
-        if args.gdb:
-            shell_command = ['gdb'] + shell_command
-
         return shell_command
 
     def _connect_to_device(self):
         device = android_commands.AndroidCommands(
             android_commands.GetAttachedDevices()[0])
         device.EnableAdbRoot()
         return device
 
     def sky_server_for_args(self, args):
         # FIXME: This is a hack.  sky_server should just take a build_dir
@@ skipping 42 matching lines @@
             port_string = 'tcp:%s' % args.command_port
             subprocess.check_call([
                 'adb', 'forward', port_string, port_string
             ])
             self.pids['remote_sky_command_port'] = args.command_port
 
         shell_command = self._build_mojo_shell_command(args)
         print ' '.join(map(pipes.quote, shell_command))
         self.pids['mojo_shell_pid'] = subprocess.Popen(shell_command).pid
 
+        if args.gdb:
+            print "Sorry, I'm not sure how best to wire up --gdb to work"
+            print "with mojo_shell as a background process.  For now use:"
+            print "gdb --pid %s" % self.pids['mojo_shell_pid']
+            shell_command = ['gdb'] + shell_command
+
         if not self._wait_for_sky_command_port():
             logging.error('Failed to start sky')
             self.stop_command(None)
         else:
             self.load_command(args)
 
     def _kill_if_exists(self, key, name):
         pid = self.pids.pop(key, None)
         if not pid:
             logging.info('No pid for %s, nothing to do.' % name)
@@ skipping 135 matching lines @@
         load_parser.set_defaults(func=self.load_command)
 
         args = parser.parse_args()
         args.func(args)
 
         self._write_pid_file(PID_FILE_PATH, self.pids)
 
 
 if __name__ == '__main__':
     SkyDebugger().main()