[clang] [clang-tools-extra] [clangd] Handle C++20 annot_module_name token and don't discard successfully built modules when on fail (PR #187858)

[Chuanqi Xu via cfe-commits]

ChuanqiXu9 wrote:

@yronglin it looks like there some problem with clangd's cache in my environment. Now I am align with you for the environment.

https://github.com/llvm/llvm-project/pull/187858