torchscript supports metacompile of ternary if
torchscript supports metacompile of ternary if

Summary: require https://github.com/pytorch/pytorch/pull/51789

Reviewed By: theschnitz

Differential Revision: D26298035

fbshipit-source-id: 284ef1c82e4274122360a6fd40656f7caef34f3b

facebookresearch/detectron2,facebookresearch/detectron2,facebookresearch/detectron2