misc/onnxruntime: fix build on armv7 and aarch64

A linux-only structure member of the cpuinfo.h API is used to determine
CPU affinity on some architectures. Use the fallback on FreeBSD, as on
platforms that do not support cpuinfo.h at all.

See also: https://github.com/microsoft/onnxruntime/issues/23181
Approved by: portmgr (build fix blanket)
MFH: 2026Q1

(cherry picked from commit d8dc35987b95f29185aa53aeb9ddd72020e6b5ff)