[crac] RFR: Fix CPUFeatures crash on new->old CPU [v5]

[Radim Vansa]

On Tue, 31 Oct 2023 00:13:23 GMT, Jan Kratochvil <jkratochvil at openjdk.org> wrote:

>> - reproducible on i7-1165G7 "qemu-kvm -cpu host" for a checkpoint and "qemu-kvm -cpu SandyBridge" for its restore
>
> Jan Kratochvil has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fix github compilation signedness problem

Sorry for keeping this waiting for a long time. In the past I wasn't sure about using `/tmp/` rather than `shm_open` target but since `os::get_temp_directory()` has this part hard-coded, too, I think it's acceptable to use that one.

I would prefer `crac_restore_finalize` to use an enum rather than a `char` but otherwise this looks good - and if it fixes some usecase, let's integrate it.

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Marked as reviewed by rvansa (Committer).

PR Review: https://git.openjdk.org/crac/pull/134#pullrequestreview-1960922290