Revert D31326599: [pytorch][PR] Compile without -Wno-unused-variable
Test Plan: revert-hammer
Differential Revision:
D31326599 (https://github.com/pytorch/pytorch/commit/a6280ab653efbf3c22e9f2dcc0dde7d22edc9a92)
Original commit changeset: 924155f1257a
fbshipit-source-id: b8ee5bc0298637443232f5ee9ec79e51ed256faf
