GHA CI: Use macOS 11 runner image

[xavier2k6]

Use macOS 11 (Big Sur) runner image.

It has now been made generally available.

Ref.: https://github.blog/changelog/2021-08-16-github-actions-macos-11-big-sur-is-generally-available-on-github-hosted-runners/

Supersedes #15195

[Chocobo1]

Perhaps we can be a little more aggressive and use macos-latest. The steps below are actually salvaged from travisci script and the details didn't change vastly.

[xavier2k6]

My original idea was to make "ALL CI Environments" use xxx-latest reference:#15355 (comment)

I am awaiting feedback about release schedule & may adopt my original idea instead.....

(I believe they make most recent OS use xxx-latest a month after general availability) but as I said.....need confirmation/feedback.

[glassez]

Isn't there any downside to losing CI for macOS 10.15? Is macOS 11 supposed to replace previous macOS versions, so that we no longer care about it? Or does a successful build on macOS 11 mean that it will also be successfully built on previous macOS?

[glassez]

@xavier2k6
Commit message should also have GHA CI: prefix.

[xavier2k6]

Isn't there any downside to losing CI for macOS 10.15?
Is macOS 11 supposed to replace previous macOS versions, so that we no longer care about it?
Or does a successful build on macOS 11 mean that it will also be successfully built on previous macOS?

Remember we are only changing the "hosted system" & not the "target" so although we may build using macOS-11 we are still targeting what is set in cmake etc which is macOS 10.15

We build on windows-2019 but our target OS is still windows 7+

[xavier2k6]

I will mark as draft until I hear back about what the update policy is from github/actions side.

[glassez]

Remember we are only changing the "hosted system" & not the "target" so although we may build using macOS-11 we are still targeting what is set in cmake etc which is macOS 10.15

Well, but then what is the real advantage? Test whether the latest build tools are able to compile it?

[xavier2k6]

Well, but then what is the real advantage? Test whether the latest build tools are able to compile it?

Yes, as well as having the latest SDK versions available for when we may change target OS to 11+

What advantage was/is there to use Ubuntu-20.04 over Ubuntu-18.04 or windows-2019 over windows-2016??

If we can change all CI's to latest we really won't have to care about this kind of thing in the future....it'll get changed automatically.

[xavier2k6]

Ok, I got some feedback from github/actions side:

Hello @xavier2k6 , usually it takes ~6 months.

Since macOS-11 was in private beta, the number of users and feedback was limited.
After GA, users has started to switch to the new OS. Before migrating -latest, we need to make sure that there is no any issues with the new image.
Another point is proper communication. We need to announce migrating latest tag beforehand because switching tag is always painful for users.

The switchover of the latest label to the most recent OS after general availability is ~6 months.

Would it be ok so @glassez @Chocobo1 @sledgehammer999 if I modify this PR or create a new one to change "ALL CI runner images" to use the xxx-latest label??

[Chocobo1]

Would it be ok so @glassez @Chocobo1 @sledgehammer999 if I modify this PR or create a new one to change "ALL CI runner images" to use the xxx-latest label??

I'm fine with {windows, macos}-latest but I still hold the same opinion for ubuntu-latest: #15355 (comment)

[xavier2k6]

FYI
For Ubuntu (only LTS) versions are used so -latest label on that system wouldn't be migrated to Ubuntu-22.04 until ~6 months after it became GA which would be around this time next year that the migration would occur.

github/actions only support 2 versions of GA OS's - we would have to move away from {Ubuntu-20.04, macOS-11 & windows-2019} at some stage in the future as these would become deprecated/removed.

We support at least 2 latest OS versions (LTS only for Ubuntu) and initiate deprecation process for the oldest one when image usage drops below 5%.

ref.: https://github.com/AlenaSviridenko/virtual-environments/blob/main/docs/software-and-images-guidelines.md#software-and-images-support-policy

-latest on all environments makes that transition convenient.

[xavier2k6]

@Chocobo1 thoughts on #15377 (comment)?

[xavier2k6]

Closing in favor of PR #15589