Segfault when using better-panic with workspaces

[vmalloc]

Managed to get a minimalistic reproduction in https://github.com/vmalloc/_segfault_reproduce.

This example segfaults once in 1-5 attempts in debug configuration.

Using stable rust (1.42.0) on MacOS 10.15.3

[vmalloc]

BTW I'm not sure the problem is with workspaces -- could be with diesel_migrations. I do know that attempting to reproduce on a single crate does not seem to yield the same result