`sync::reentrant_init` fails when using `cargo test --all-targets`

[Simon Chopin]

For some reason, cargo test --all-targets doesn't build the examples in the same way it would without this option, which breaks the tests. I'm not sure if it is a bug in cargo itself, so I'm reporting this here.

[Alex Kladov]

Can no longer reproduce this, but yeah, this stuff is tricky