CI failure on 5.1 32-bit builders

[edwintorok]

Context

OCaml-CI was working fine last week: https://github.com/edwintorok/dune-compiledb/runs/19665064351
However today I noticed failures that have nothing to do with my code: https://github.com/edwintorok/dune-compiledb/runs/19895068888

There are only 2 configurations that fail (all others pass):
https://ocaml.ci.dev/github/edwintorok/dune-compiledb/commit/85fabc2e28ddad42ad66b5eec85f5d881cda9556/variant/debian-12-5.1_arm32_opam-2.1/-/refs/pull/2/head
https://ocaml.ci.dev/github/edwintorok/dune-compiledb/commit/85fabc2e28ddad42ad66b5eec85f5d881cda9556/variant/debian-12-5.1_x86_32_opam-2.1/-/refs/pull/2/head

They both fail like this:

[ERROR] ocaml-base-compiler = 5.1.0 not available because the package is pinned to version 5.1.1

These 2 configuration appear to be new, they are not there in the CI run from a week ago.

Step(s) to reproduce

https://github.com/edwintorok/dune-compiledb/runs/19895068888

Expected behaviour

CI doesn't raise version error about compiler.
If these 2 configurations are still experimental please mark them as such so they don't cause the entire CI to report a failure.

Technical details

Additional context

Screenshots

[edwintorok]

FWIW my project says (ocaml (>= 4.08)) so the 5.1.0 vs 5.1.1 must be something inside the CI that goes wrong.