Replace pkg-config with pkgconf when the distribution is brew

[mseri]

Import #26878 with only the latest pkg-config-file updated (in case there are users still using older copies of homebrew)

[mseri]

This was already tested

[hannesm]

First of all, thanks for your work on the opam-repository maintenance :)

Hmm, I'd have expected to bump conf-pkg-config in the version number... now it is unclear when someone reports a failure in conf-pkg-config.3 what their brew depext candidate is/was.

Furthermore, from my brief understanding, a recompilation for everybody using conf-pkg-config could have been avoided by bumping the version number (conf-pkg-config.3.1) and mark that as available: ... = os = "macos" & os-distribution = "homebrew"}.

But I may be wrong, I'm a bit unhappy about unversioned conf-* package upgrades in general (adding distributions is usually not an issue, but modifying existing filters etc. is dangerous - I remember some breakage in the past), but if this is considered to be a good idea, please go ahead.

[mseri]

You are right, of course. The reason I decided not to bump the version in this case, is that almost every macOS user that uses homebrew uses the head of their packages branch. For all the others, who would see a failure with the new release, pending to 3.1 or to 2 would give the exact same package. So I thought maybe this is one of those points in which we can avoid creating a new package since version 2 would be exactly equivalent for those user to version 2. With metadata changes if this type this is something we have done other times. But I agree, maybe we should’ve just done a new version to avoid any confusion.

[mseri]

Furthermore, from my brief understanding, a recompilation for everybody using conf-pkg-config could have been avoided by bumping the version number (conf-pkg-config.3.1) and mark that as available: ... = os = "macos" & os-distribution = "homebrew"}.

I thought with recent opams this should not happen unless you are on the system that was affected by the change. But I am absolutely not sure about it 😅

[SkySkimmer]

This seems to have broken our CI and the fix I found looks a bit strange https://github.com/coq/coq/pull/19836/files
Are we doing something wrong?