[OpenMP] Avoid warnings about unused static functions on windows

Add ifdefs around one function that only is used in unix build

Add a void cast for a windows specific function that currently is
unused but may be intended to be used at some point.

Differential Revision: https://reviews.llvm.org/D96584

GitOrigin-RevId: 16428a8d91a904c841086a971a8f26c3d8cf1307
2 files changed