Improve segaddr fixing for 32-bit destructors

Summary: CMake actually mangles this line in ways we don't want it to.
Use the commas to mangle it in ways we DO want it to.

Reviewed By: @paulbiss

Differential Revision: D1686486

Signature: t1:1686486:1416274212:df33c36917486ed85f46d805b0c5b48956edf314