miri no longer builds after rust-lang/rust#98486

[rust-highfive]

Hello, this is your friendly neighborhood mergebot.
After merging PR #98486, I observed that the tool miri has failing tests.
A follow-up PR to the repository https://github.com/rust-lang/miri is needed to fix the fallout.

cc @matthiaskrgr, do you think you would have time to do the follow-up work?
If so, that would be great!

[RalfJung]

command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2-tools-bin/miri" "--edition" "2018" "-Astable-features" "--sysroot" "/home/user/.cache/miri/HOST" "-Zui-testing" "tests/pass/concurrency/sync.rs" "--error-format=json" "-Zmiri-disable-isolation" "-Zmiri-strict-provenance"
Pass got exit status: 1
actual output differed from expected tests/pass/concurrency/sync.stderr
Diff< left / right > :
>error: the main thread terminated without waiting for all remaining threads
>
>note: pass `-Zmiri-ignore-leaks` to disable this check
>
>error: aborting due to previous error

Probably a missing join (these tests are a bit random, now that we have preemption).