[OpenMP][libomp] Add support for offline CPUs in Linux

If some CPUs are offline, then make sure they are not included in the
fullMask even if norespect is given to KMP_AFFINITY.

Differential Revision: https://reviews.llvm.org/D112274

GitOrigin-RevId: 1dd797168e9f8cb592c254c642f196dab3447092
3 files changed