fix gdb_bthread_stack bthread_begin error (#3176)

Co-authored-by: Haigang Xi <[email protected]>

Author: Searion

tools/gdb_bthread_stack.py

@@ -55,8 +55,8 @@
 status = False
 
 def get_bthread_num():
-    root_agent = gdb.parse_and_eval("&(((((*bthread::g_task_control)._nbthreads)._combiner)._agents).root_)")
-    global_res = int(gdb.parse_and_eval("((*bthread::g_task_control)._nbthreads)._combiner._global_result"))
+    root_agent = gdb.parse_and_eval("&(((*(((*bthread::g_task_control)._nbthreads)._combiner._M_ptr))._agents).root_)")
+    global_res = int(gdb.parse_and_eval("(*(((*bthread::g_task_control)._nbthreads)._combiner._M_ptr))._global_result"))
     get_agent = "(*(('bvar::detail::AgentCombiner<long, long, bvar::detail::AddTo<long> >::Agent' *){}))"
     last_node = root_agent
     long_type = gdb.lookup_type("long")