caffe2 missing cctype header (#46052)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/46052
`<cctype>` is what provides `isuppper`, etc.
https://en.cppreference.com/w/cpp/header/cctype
clang on windows complaining about the missing header.
Test Plan: CI green
Reviewed By: yinghai
Differential Revision: D24201925
fbshipit-source-id: 7b242200f09c30bf78dde226e14ee4be71758b87
