Error if pocketfft is not found (#67909)
Summary:
Fixes https://github.com/pytorch/pytorch/issues/67842
cc mruberry peterbell10
Pull Request resolved: https://github.com/pytorch/pytorch/pull/67909
Reviewed By: albanD
Differential Revision: D33759534
Pulled By: malfet
fbshipit-source-id: 03548c95fe233b812b303ce9603c20ff9f626c39
(cherry picked from commit 214624e254770b1b160d30b000cc244b0c8601b4)
