./reinit coordination

Issue for tracking the various parts involved in the reinit transition

There are currently two wrapper repositories pacxx-llvm2 and pacxx-rv2 that fetch the real repository and apply patches. They do so using a script reinit. The patched target repository minus its git metadata ends up in the same directory the wrapper repository was checked out to. This has several drawbacks:

• In the ci it means we have no way to report exactly what was checked out for the target repository
• Updating the wrapper repository involves temporarily modifying reinit and restoring it later

After the transition, reinit will take the directory to put the target repository into as an argument; if no argument is given either ../llvm or ../llvm/tools/rv will be assumed.

reinit providers:

• https://zivgitlab.uni-muenster.de/HPC2SE-Project/pacxx-llvm2 (#1, !4)
• https://zivgitlab.uni-muenster.de/HPC2SE-Project/pacxx-rv2 (#1, #2, !1)

reinit users:

• https://zivgitlab.uni-muenster.de/HPC2SE-Project/pacxx (!1)
• https://gitlab.dune-project.org/joe/pacxx-docker (!54 (merged))
• https://zivgitlab.uni-muenster.de/HPC2SE-Project/pacxx-runtime (!29)