[ROCm] allow user to override PYTORCH_ROCM_ARCH (#60602)
Summary:
Restores the ability of a user to call .jenkins/pytorch/build.sh while
also setting PYTORCH_ROCM_ARCH. Otherwise, with IN_CI=1 as the new
default, it will forcibly ignore user settings when build.sh is used
outside of CI.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/60602
Reviewed By: samestep
Differential Revision: D29490791
Pulled By: janeyx99
fbshipit-source-id: b5e8a529b8e0b5020b260b4bf027a37e0c1df8d5
