[Bug] Clang 19 compilation failure

Tái hiện lỗi trên Fedora 41 bằng các lệnh của workspace-automation và kiểm tra third_party/flatbuffers/include/flatbuffers/flatbuffers.h, đặc biệt là các phép gán quanh các dòng 834, 1002 và 1874. Kiểm tra đường dẫn biên dịch liên quan thông qua external/src/flatbuffers/src/reflection.cpp và xác nhận rằng Firebase C++ SDK được build thành công với Clang 19 mà không gặp lỗi deleted-operator.

[REQUIRED] Please fill in the following fields:

• Pre-built SDK from the website or open-source from this repo: source
• Firebase C++ SDK version: v12.5.0
• Problematic Firebase Component: third_party - flatbuffers
• Other Firebase Components in use: Cloud, Auth, Storage, common
• Platform you are using the C++ SDK on: Ubuntu 20 to Linux Fedora 41
• Platform you are targeting: desktop, embedded Linux (Yocto)

[REQUIRED] Please describe the issue here:

SDK fails to build with Clang 19 (Fedora 41). With minimal patch it builds fine on Clang 10 (Ubuntu 20).

This error will be repeated Nx depending on CPU count used in build:

In file included from /mnt/raid10/workspace-automation/app/firebase-cpp-sdk/cmake-build-release/external/src/flatbuffers/src/reflection.cpp:17:
In file included from /mnt/raid10/workspace-automation/app/firebase-cpp-sdk/cmake-build-release/external/src/flatbuffers/include/flatbuffers/reflection.h:25:
In file included from /mnt/raid10/workspace-automation/app/firebase-cpp-sdk/cmake-build-release/external/src/flatbuffers/include/flatbuffers/reflection_generated.h:7:
/mnt/raid10/workspace-automation/app/firebase-cpp-sdk/cmake-build-release/external/src/flatbuffers/include/flatbuffers/flatbuffers.h:1874:12: error: overload resolution selected deleted operator '='
 1874 |       buf_ = other.buf_;
      |       ~~~~ ^ ~~~~~~~~~~
/mnt/raid10/workspace-automation/app/firebase-cpp-sdk/cmake-build-release/external/src/flatbuffers/include/flatbuffers/flatbuffers.h:1002:44: note: candidate function has been explicitly deleted
 1002 |   FLATBUFFERS_DELETE_FUNC(vector_downward &operator=(const vector_downward &))
      |                                            ^
/mnt/raid10/workspace-automation/app/firebase-cpp-sdk/cmake-build-release/external/src/flatbuffers/include/flatbuffers/flatbuffers.h:834:20: note: candidate function not viable: expects an rvalue for 1st argument
  834 |   vector_downward &operator=(vector_downward &&other) {
      |                    ^         ~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.

Steps to reproduce:

Fedora 41

git clone https://github.com/meta-flutter/workspace-automation
cd workspace-automation
./flutter_workspace.py --enable=firebase-cpp-sdk