fake the libcxxabi type-info shim
fake the libcxxabi type-info shim

Summary: The actual shim type may sometimes not be linkable. So fake it - as long as the vtable is the same, it should not make a difference.

Reviewed By: luciang

Differential Revision: D28216291

fbshipit-source-id: 8c493a207cfb5414684147ddb850835bc0965bc5

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