fa1565a7

By: Lucien Huber <im@lcnbr.ch>

preserve vendored symbolica build reuse

Symbolica 3.0 watches .git/HEAD, which its published registry crate omits.
Supply the same stable marker used for the previous Git dependency through
Crane's registry hook, scoped to this affected version.

The targeted producer/consumer build now compiles only workspace-hack in
0.55s after restoration; previously Symbolica recompiled for 4m12s.

User request:
symbolica 3.0 is now on crates. Lets use that