Merge branch 'use-dedicated-caches' into 'master'

ref:infrastructure/dune-website This should fix the problem of `git worktree`
failing when reusing the cache from a different job.

Fixes [#69], [#70].

See merge request [!231]

  [#69]: gitlab.dune-project.org/NoneNone/issues/69
  [#70]: gitlab.dune-project.org/NoneNone/issues/70
  [!231]: gitlab.dune-project.org/infrastructure/dune-website/merge_requests/231


Closes #70 and #69