GHSA-wcg3-cvx6-7396

### Impact

Unix-like operating systems may segfault due to dereferencing a dangling pointer in specific circumstances. This requires an environment variable to be set in a different thread than the affected functions. This may occur without the user's knowledge, notably in a third-party library.

The affected functions from time 0.2.7 through 0.2.22 are:

- `time::UtcOffset::local_offset_at` - `time::UtcOffset::try_local_offset_at` - `time::UtcOffset::current_local_offset` - `time::UtcOffset::try_current_local_offset` - `time::OffsetDateTime::now_local` - `time::OffsetDateTime::try_now_local`

The affected functions in time 0.1 (all versions) are:

- `at` - `at_utc` - `now`

Non-Unix targets (including Windows and wasm) are unaffected.

### Patches

In some versions of `time`, the internal method that determines the local offset has been modified to always return `None` on the affected operating systems. This has the effect of returning an `Err` on the `try_*` methods and `UTC` on the non-`try_*` methods. In later versions, `time` will attempt to determine the number of threads running in the process. If the process is single-threaded, the call will proceed as its safety invariant is upheld.

Users and library authors with time in their dependency tree must perform `cargo update`, which will pull in the updated, unaffected code.

Users of time 0.1 do not have a patch and must upgrade to an unaffected version: time 0.2.23 or greater or the 0.3 series.

### Workarounds

Library authors must ensure that the program only has one running thread at the time of calling any affected method. Binary authors may do the same and/or ensure that no other thread is actively mutating the environment.

### References

[time-rs/time#293](https://github.com/time-rs/time/issues/293).