gh-120831: Increase the default minimum supported iOS version to 13.0

[freakboy3742]

Bumps the default minimum iOS version from 12.0 to 13.0.

As discussed on #120831, the previous default value of 12.0 worked successfully at runtime, but raised a compilation warning about the usage of an SQLite API that wasn't added until iOS 13.0. Although protection exists in the code to prevent any runtime problem, avoiding the compilation warning was judged to be more important.

The usage of iOS 12 is estimated to be less that 0.5% of the total iOS install base, so the impact on the user base is minor. It's also only a default version; it's possible to manually configure any minimum version at compile time.

In addition to increasing the default minimum version, this PR modifies the logging generated by the configure script to be more explicit about the iOS deployment target (aka minimum version) that will be used. It also adds usage documentation about the default iOS supported version.

The buildbot will still generate the warning because it the iOS buildbot configuration currently hard-codes the 12.0 minimum supported version. I'll push an update for the buildbot configuration shortly.

Fixes #120831.

• Issue: ios buildbot failure: enclose 'sqlite3_create_window_function' in a __builtin_available check to silence this warning #120831

---

📚 Documentation preview 📚: https://cpython-previews--121250.org.readthedocs.build/

[freakboy3742]

!buildbot iOS

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @freakboy3742 for commit 20209cd 🤖

The command will test the builders whose names match following regular expression: iOS

The builders matched are:

• iOS ARM64 Simulator PR

[freakboy3742]

!buildbot iOS

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @freakboy3742 for commit 20209cd 🤖

The command will test the builders whose names match following regular expression: iOS

The builders matched are:

• iOS ARM64 Simulator PR

[freakboy3742]

The new buildbot configuration has been deployed; this build shows an auto detected iOS 13 minimum, and no build warnings (compared to the previous PR build, which shows 2 warnings associated with the SQLite issue).

[erlend-aasland]

Looks good, with a tiny nit.

[freakboy3742]

!buildbot iOS

[freakboy3742]

!buildbot iOS

[zware]

!buildbot iOS

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @zware for commit cbd760e 🤖

The command will test the builders whose names match following regular expression: iOS

The builders matched are:

• iOS ARM64 Simulator PR

[zware]

Found how I broke it...

[freakboy3742]

!buildbot iOS

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @zware for commit cbd760e 🤖

The command will test the builders whose names match following regular expression: iOS

The builders matched are:

• iOS ARM64 Simulator PR

[freakboy3742]

!buildbot iOS

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @freakboy3742 for commit cbd760e 🤖

The command will test the builders whose names match following regular expression: iOS

The builders matched are:

• iOS ARM64 Simulator PR

[miss-islington-app]

Thanks @freakboy3742 for the PR 🌮🎉.. I'm working now to backport this PR to: 3.13.
🐍🍒⛏🤖

[bedevere-app]

GH-121833 is a backport of this pull request to the 3.13 branch.

[freakboy3742]

For posterity - merged despite the CI failures. The CI failures are due to #121832; local testing and inspection of the CI logs demonstrates that the new minimum version is being applied.