Use global PIC flag for XNNPACK (#93896)
Summary:
- XNNPACK Object libraries needs an explicit PIC flag when building static, PIC libXNPACK.a
- Without this link process runs into relocation errors
- Using this global switch to avoid updating XNNPACK CMake
Test Plan: CI
Differential Revision: D42944764
Pull Request resolved: https://github.com/pytorch/pytorch/pull/93896
Approved by: https://github.com/Skylion007, https://github.com/Neilblaze, https://github.com/salilsdesai
