brew: disable compat mode when running sw_vers

[gromgit]

As far as I can tell, Homebrew believes Big Sur == 11.x, so we should make sure sw_vers doesn't output 10.16.

Addresses Homebrew/discussions#941

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[BrewTestBot]

Review period will end on 2021-03-02 at 00:00:00 UTC.

[Bo98]

Thinking about this again, I forgot that env filtering is applied here. How did this env manage to slip through that?

[gromgit]

I forgot that env filtering is applied here. How did this env manage to slip through that?

That's...a very good question. 😕

In any event, I've added another fix, to strip everything but major version from HOMEBREW_MACOS_VERSION for Big Sur and later. Big Sur versions now have patchlevel numbers, so the current code incorrectly strips 11.2.1 down to 11.2.

[Bo98]

to strip everything but major version from HOMEBREW_MACOS_VERSION for Big Sur

I'm not entirely sure about this code - we don't strip any patch versions for earlier macOS versions.

Seems a bit weird and inconsistent to make this be the major version only while the earlier versions still have the full 10.15.7.

[gromgit]

AFAICT, HOMEBREW_OS_VERSION (which becomes OS_VERSION in Ruby-land) is just a label that's added to various diagnostics outputs, so I guess it's not a critical issue. I'm just making sure the code agrees with the associated comment. 😁

[MikeMcQuaid]

Thinking about this again, I forgot that env filtering is applied here. How did this env manage to slip through that?

Yeh, this.

I think I'd like to hold off here until we see at least one other person with this problem.

[BrewTestBot]

Review period ended.

[MikeMcQuaid]

Want to wait to see at least one other person with this problem.

[BrewTestBot]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.