linux/diagnostic: add check for versioned GCC linkage

[carlocab]

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This complements my other two GCC-on-Linux PRs (#13631, #13633), however they are both reliant on bottles eventually being (re-)poured.

Let's try to speed that up by returning an error message from brew doctor whenever a user has formulae installed that would benefit from a brew reinstall.

[BrewTestBot]

Review period will end on 2022-08-04 at 13:00:15 UTC.

[carlocab]

As before, I still need to test this. But this is the proof-of-concept.

[Bo98]

Is this for the scenario where the user doesn't use brew update?

[carlocab]

I'll admit to not having thought too carefully about failure modes yet: my motivation is that it would be good to provide as many paths to brew reinstall as possible to minimise breakage.

Something like this (omitting the #core_tap? check) might help for your concern over source-built formulae from https://github.com/Homebrew/brew/pull/13633#issuecomment-1203951369, though.

[BrewTestBot]

Review period ended.

[carlocab]

Benchmarked:

Before

Command	Mean [s]	Min [s]	Max [s]	Relative
brew doctor	5.248 ± 0.053	5.166	5.328	1.00

After

Command	Mean [s]	Min [s]	Max [s]	Relative
brew doctor	2.915 ± 0.033	2.862	2.957	1.00

This is on a system with about ~430 formulae installed, which is pretty extreme.

This means brew doctor is nearly twice as slow as before, which is pretty bad. OTOH, it didn't take long at all to run before, so it's not too bad in the end.

[MikeMcQuaid]

This means brew doctor is nearly twice as slow as before, which is pretty bad. OTOH, it didn't take long at all to run before, so it's not too bad in the end.

Yeh, I think that's too slow to run for everyone every time 😭.

[carlocab]

Running some slightly more comprehensive benchmarks here: https://github.com/carlocab/workflow-test/actions/runs/2805207136/attempts/1#summary-7696068383

One of the runs is still going, but the ones that finished are a bit all over the place.

I'm ok to leave this be for now. We can reconsider it depending on the number of users who report issues that might be helped by this.

[MikeMcQuaid]

I'm ok to leave this be for now. We can reconsider it depending on the number of users who report issues that might be helped by this.

Shouldn't this be handled automatically by brew update? If so, can we check if the setting is set, make this a no-op if so and tell them to run brew update if anything fails? Similarly, we could make it fail the first time we find a single failure rather than getting all the failures from all formulae.

[MikeMcQuaid]

Let's ship this and revert if it's causing issues/too slow.