Error recompiling mingw-w64-shims when using setup-ocaml in CI

[Gbury]

I was trying to update the CI configuration of one of my projects (cf https://github.com/Gbury/dolmen ), and I happened upon the following error:

#=== ERROR while installing mingw-w64-shims.0.2.0 =============================#
Cannot copy D:\a\dolmen\dolmen\_opam\.opam-switch\build\mingw-w64-shims.0.2.0\shim.exe to D:\a\dolmen\dolmen\_opam\bin\cygpath.exe (C:\hostedtoolcache\windows\opam\2.3.0\x86_64\opam.exe: "open" failed on D:\a\dolmen\dolmen\_opam\bin\cygpath.exe: Permission denied).

See https://github.com/Gbury/dolmen/actions/runs/13902947999/job/38899007827?pr=230 for the full log (I'm also attaching the raw log text file, just in case the log on the github interface disappears : ci_shims_error.txt ).

The error seems to be because mingw-w64-shims is being recompiled, seemingly because it [uses conf-pkg-config] which is being isntalled because of zarith. However, the very weird thing with that error is that another run of the same CI (but with very slightly different configuration options, i.e. just adding flambda for the switch) actually succeeded, cf https://github.com/Gbury/dolmen/actions/runs/13902947999/job/38899007846?pr=230 .

I'm a bit lost on how to solve this, and whether it's something that I should (or could) fix in my workflow files, or if it's something that needs a fix from upstream ?

[Gbury]

Oh.. looks like triggering a re-run of the job solved the problem... I'm guessing the problem might have been related to the caching done automatically by setup-ocaml maybe ?