Remove support for old architectures in cpp_extension and CMake (#24442)
Summary:
This is a follow-up to gh-23408. No longer supported are any arches < 3.5 (numbers + 'Fermi' and 'Kepler+Tegra').
Pull Request resolved: https://github.com/pytorch/pytorch/pull/24442
Differential Revision: D16889283
Pulled By: ezyang
fbshipit-source-id: 3c0c35d51b7ac7642d1be7ab4b0f260ac93b60c9
