Reland `sigsetjmp` patches with build fixes.
We wrap every target replying on the epilogue library into conditional
checks.
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Co-authored-by: Petr Hosek <phosek@google.com>
This reverts commit f07511a0e0d2ac9bee9ae12a9ad68e279e352634.
This reverts commit 5bb4cf9d9189c41de50adffd960eb2188140eb9c.
It caused a CMake configuration issue.