[hack] make hack fallback to lstat if dirent provides DT_UNKNOWN
[hack] make hack fallback to lstat if dirent provides DT_UNKNOWN

Reviewed By: samwgoldman

Differential Revision: D18217903

fbshipit-source-id: 3d5fe7934eb0dc06511aea974c7e3346cd0e76ee

nmote/flow,nmote/flow,nmote/flow,nmote/flow,nmote/flow,nmote/flow,nmote/flow