threading_posix: don't delete thread_local thread object

Disabling on exit thread delete as it causes an assert fail.
There isn't a leak here because current_thread_ is a thread_local static.

src/xenia/base/threading_posix.cc

@@ -1007,7 +1007,10 @@ Thread* Thread::GetCurrentThread() {
   pthread_t handle = pthread_self();
 
   current_thread_ = new PosixThread(handle);
-  atexit([] { delete current_thread_; });
+  // TODO(bwrsandman): Disabling deleting thread_local current thread to prevent
+  //                   assert in destructor. Since this is thread local, the
+  //                   "memory leaking" is controlled.
+  // atexit([] { delete current_thread_; });
 
   return current_thread_;
 }