Fixed gcd to use 64 bit integers (#21041)
Summary:
Not much to say. Fixes implementation introduced here: https://github.com/pytorch/pytorch/pull/19115
Pull Request resolved: https://github.com/pytorch/pytorch/pull/21041
Differential Revision: D15528801
Pulled By: Chillee
fbshipit-source-id: bacd709eb711ca00156bd70480d6051b437517ed
