* etc/time-travel-manifest.scm (<guix-instance-compiler>): Use a separate
cache per system so that parallel system evaluations do no step on each
other's toes.
This manifest makes it easy to test travels from the current revision
back to the revision of a past Guix release.
Suggested by zimoun <zimon.toutoune@gmail.com>.
* etc/time-travel-manifest.scm: New file.
* Makefile.am (EXTRA_DIST): Add it.
Ludovic Courtès
Mathieu Othacehe