[libcxx-commits] [libcxxabi] [libc++abi] Revert gating of `__cxa_thread_atexit` on Linux||Fuchsia (PR #186054)

[Nikolas Klauser via libcxx-commits]

https://github.com/philnik777 commented:

This change was based on the fact that `cxxabi.h` guards this function behind `#if defined(__linux__) || defined(__Fuchsia__)`. If this is wrong, that header needs to be updated as well. However, it's not clear to me at all which platforms actually expect this function if it's not declared on platforms that use it (probably through compiler magic?).

https://github.com/llvm/llvm-project/pull/186054