Per rustsec/advisory-db#1190, it would be good to move to a policy where
we don't file advisories against crates which perform unsynchronized
reads from the process environment, and instead focus only on crates
which modify the process environment in an unsynchronized manner.
This is an advisory similar to `RUSTSEC-2020-0071` impacting usages of
`localtime_r` within `chrono` itself, since the API is used in a
cross-thread manner in an unsound way.
