[OpenMP] Allow affinity to re-detect for child processes

Current atfork() handler for child processes does not reset
the affinity masks array which prevents users from setting their own
affinity in child processes.

Differential Revision: https://reviews.llvm.org/D99218

GitOrigin-RevId: 5ebbb366c4a369740c3a3fe1f673e0e8c1902e60
3 files changed