Module linux_like

Destructor registration for Linux-like systems.

Since what appears to be version 2.18, glibc has shipped the __cxa_thread_atexit_impl symbol which GCC and clang both use to invoke destructors in C++ thread_local globals. This function does exactly what we want: it schedules a callback which will be run at thread exit with the provided argument.

Unfortunately, our minimum supported glibc version (at the time of writing) is 2.17, so we can only link this symbol weakly and need to use the list destructor implementation as fallback.