[OpenMP] Make sure the Thread ID function is not removed

Summary:
The thread ID function was reintroduced in D110195, but could
potentially be removed by the optimizer. Make the function noinline to
preserve the call sites and add it to the externalization RAII so its
definition is not removed by the attributor.
GitOrigin-RevId: 1cf86df8839ae2c8ebb7c68e1c355ec960a153cf
2 files changed