Mac ARM64 5.1.0~rc2 upgrade failure

[jmid]

It looks like the docker image for Mac ARM64 5.1 was upgraded to 5.1.0~rc2 🎉
It fails now however:
https://ocaml-multicoretests.ci.dev:8100/job/2023-08-31/200021-ci-ocluster-build-7f7193#L65

[WARNING] Upgrade is not possible because of conflicts or packages that are no longer available:
    - Missing dependency:
    - ocaml-base-compiler >= 5.1.0~rc2
    incompatible with the switch invariant ["ocaml-base-compiler" {= "5.1.0~rc2"}] (use `--update-invariant' to force)

I think it just needs an opam update to receive the latest opam-repo that includes the 5.1.0~rc2 release...

[jmid]

Figured out a fix with help from @mtelvers

It would be nice to set the validity of the opam-repository to a week or so, to allow for picking up updates such as ocaml.5.1.0~rc2 and the recent qcheck.0.21.2 without having to restart the service.

[jmid]

We just hit this issue again with the update to 5.1.0~rc3:
https://ocaml-multicoretests.ci.dev:8100/job/2023-09-07/103019-ci-ocluster-build-081d5f#L67

/: (run (cache (opam-archives (target /Users/mac1000/.opam/download-cache)) (homebrew (target /Users/mac1000/Library/Caches/Homebrew)))
        (network host)
        (shell "cd ~/opam-repository && (git cat-file -e 7a76ea59a3009358e12f34ba7cd690f940353705 || git fetch origin master) && git reset -q --hard 7a76ea59a3009358e12f34ba7cd690f940353705 && git log --no-decorate -n1 --oneline && opam update -u"))
7a76ea59a3 Merge pull request #24353 from dinosaure/release-miou-v0.0.1_beta1

<><> Updating package repositories ><><><><><><><><><><><><><><><><><><><><><><>
[default] synchronised from git+file:///Users/mac1000/opam-repository

[WARNING] Upgrade is not possible because of conflicts or packages that are no longer available:
    - Missing dependency:
    - ocaml-base-compiler >= 5.1.0~rc3
    incompatible with the switch invariant ["ocaml-base-compiler" {= "5.1.0~rc3"}] (use `--update-invariant' to force)

It was temporarily solved by restarting the service.
As we will face the same issue next week with the release of 5.1.0 (and later for a 5.2.0* release cycle) it would be nice to lower the cache entry validity to avoid the need for continued manual intervention.