Add use_rocm flag to detect AMD build in the runtime (#21718)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/21718
adding a detection method on whether the package is built for AMD.
Reviewed By: bddppq
Differential Revision: D15795893
fbshipit-source-id: 91a21ee76b2273b1032507bdebe57e016717181d
