move 8.8.4 and 8.6.5 to the old-ghcs run

[geekosaur]

Github has moved macos-latest to macos-14 on ARM, so those jobs can't find a working ghc (ARM support started in 8.10.5). The alternative is to split the main validate run in half so that 8.6 and 8.4 can be run on macos-13 instead of macos-latest.

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[geekosaur]

Does anyone know why there's a bootstrap job on OS X? I thought generating the bootstrap plans didn't need to be done on multiple OSes.

The reason I ask is that apparently the macos-14 runner doesn't have ghcup preinstalled, so something will need to be done there to install it.

ETA: it's also missing LLVM.

[ulysses4ever]

I didn't think it's the right approach to move the 8.8 or 8.6 anywhere, as it is done here, because they're in our support window. I think it should be done though include/exclude as in #9949

[Mikolaj]

@geekosaur

Does anyone know why there's a bootstrap job on OS X? I thought generating the bootstrap plans didn't need to be done on multiple OSes.

I think CI tests the actual bootstrapping (building using the bootstrap plans). I don't think we have a CI job that tests boostrap plan generation, which is a pity (we discover PRs that break it too late).

@ulysses4ever

I didn't think it's the right approach to move the 8.8 or 8.6 anywhere, as it is done here, because they're in our support window.

I know what you mean, but formally, the window means we should not exclude nor break the GHCs in cabal, not in CI. As I've mentioned on the channel repeatedly in the last week, when discussion the unbearable slowness of OSX CI jobs and the upcoming macos-14 breakage, we should consider removing some OSX CI jobs unless macos-14 can run them and speeds them up enough.