Support 32-bit Windows in exception wrapper
Support 32-bit Windows in exception wrapper

Summary:
It's easy enough to calculate the right offset for both 32 and 64-bit
platforms, so we can just do so instead of hardcoding the 64-bit offset.

Reviewed By: yfeldblum, Orvid

Differential Revision: D7377039

fbshipit-source-id: 5f7efbae58b7694801274e195a97b5e5b62b5a5e

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