[libc-commits] [libc] [libc] Provide empty definitions for `teardown_main_tls` symbols (PR #173412)

[Petr Hosek via libc-commits]

petrhosek wrote:

> This is easy to approve for the `teardown_main_tls` symbol, but might require more discussion wrt `__cxa_thread_finalize`. So let's make it two separate changes, and use the second one to more thoroughly discuss issues with the `__cxa_thread_finalize` symbol name / ABI in particular.

I updated this change to only cover `teardown_main_tls` and will make a separate pull request for `__cxa_thread_finalize`.

https://github.com/llvm/llvm-project/pull/173412