Fix `sccache not being used on Windows` (#21248)
Summary:
Fixes https://github.com/pytorch/pytorch/issues/21167.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/21248
Differential Revision: D15592742
Pulled By: soumith
fbshipit-source-id: 4add002698c13301f142526cd783c866d345bf5e
