gdb: add some additional debug output in remote.c

I needed more debug output from:
  remote_target::select_thread_for_ambiguous_stop_reply
I thought this would be useful for others too.

gdb/ChangeLog:

	* remote.c (remote_target)
	<select_thread_for_ambiguous_stop_reply>: Add additional debug
	output.

gdb/remote.c

@@ -7934,12 +7934,16 @@ ptid_t
 remote_target::select_thread_for_ambiguous_stop_reply
   (const struct target_waitstatus *status)
 {
+  REMOTE_SCOPED_DEBUG_ENTER_EXIT;
+
   /* Some stop events apply to all threads in an inferior, while others
      only apply to a single thread.  */
   bool process_wide_stop
     = (status->kind == TARGET_WAITKIND_EXITED
        || status->kind == TARGET_WAITKIND_SIGNALLED);
 
+  remote_debug_printf ("process_wide_stop = %d", process_wide_stop);
+
   thread_info *first_resumed_thread = nullptr;
   bool ambiguous = false;
 
@@ -7959,6 +7963,10 @@ remote_target::select_thread_for_ambiguous_stop_reply
 	ambiguous = true;
     }
 
+  remote_debug_printf ("first resumed thread is %s",
+		       pid_to_str (first_resumed_thread->ptid).c_str ());
+  remote_debug_printf ("is this guess ambiguous? = %d", ambiguous);
+
   gdb_assert (first_resumed_thread != nullptr);
 
   /* Warn if the remote target is sending ambiguous stop replies.  */