Update buildbot to use XCframework build script.

[freakboy3742]

The iOS XCframework build script will shortly be moved to Platforms/iOS.

This updates the Buildbot config to use the new XCframework buildbot in "slow" mode for 3.15+ builds, and falls back to the old build script for 3.13 and 3.14 builds.

I haven't pushed the corresponding CPython PR yet; this is to explore options for branch-based configuration of the build script.

As I currently understand it, this will work for buildbot runs that are triggered on a merge of a PR on main, 3.13, 3.14, or the 3.15 branch (when it is forked). A PR build will succeed on main and 3.15 (when it is forked). But a PR build based off a 3.13/3.14 branch will fail (because there's currently no way to identify the base branch of a PR job).

[vstinner]

But a PR build based off a 3.13/3.14 branch will fail (because there's currently no way to identify the base branch of a PR job).

Correct. IMO it's an acceptable trade-off. I don't see any simple solution using buildbot API to use different steps depending on an actual check run on the worker (ex: check if Platforms/Apple exists).

SetPropertyFromCommand() and util.Interpolate() can only be used to pass a string to a command, not really to use very different steps and commands (as you do in this PR).

[encukou]

It's probably not worth worrying about 3.13.

For 3.14, maybe do something like [ -e Platforms/Apple ] || (mkdir -p Platforms; ln -s ../Apple Platforms/Apple) for the custom?

[freakboy3742]

It's probably not worth worrying about 3.13.

👍

For 3.14, maybe do something like [ -e Platforms/Apple ] || (mkdir -p Platforms; ln -s ../Apple Platforms/Apple) for the custom?

Good idea - I'll push an update shortly.