`Condvar` hangs in newer rust versions

[mkroening]

rusty-demo hangs in QEMU as well as uhyve since nightly-2022-06-05: rust-lang/rust@a6b8c69...4e725ba

There are only 'skip'ped commits left to test.
The first bad commit could be any of:
6a417d482899e13b1fbef5f5f9962f59e89e9e53
ac5aa1ded529cd8317b351ba952ff9cd78b1e172
e9ec02267a0b84d6a17357c1a0da46093ba5ad1d
We cannot bisect more!

[mkroening]

This is caused by rust-lang/rust#97647.