gh-141692: Add a slice-specific lib folder to iOS XCframeworks.

[freakboy3742]

Adds a lib folder to each slice of an iOS XCframework that contains a libpython*.dylib symlink to the underlying Framework dylib.

This mirrors the structure of macOS frameworks, allowing iOS binary modules to be compiled with -L path/to/python/lib -lpython, rather than requiring -F path/to/Framework -framework Python. This increases compatibility with standard Unix tooling for building binary modules.

The libpython*.dylib must be explicitly excluded from being copied into the architecture-specific library folders, so that the dylib (or a symlink) won't be copied into the app binary.

The final structure of a full XCframework will look something like:

• Python.xcframework
  • lib
    • cross-platform copy of the standard libray
  • ios-arm64
    • include
    • lib
      • libpython.dylib - link to ../Python.framework/Python
    • lib-arm64
      • arm64 device-specific standard library parts (sysconfig, build-details.json etc)
    • Python.framework
  • ios-arm64_x86_64-simulator
    • include
    • lib
      • libpython.dylib - link to ../Python.framework/Python
    • lib-arm64
      • arm64 simulator-specific standard library parts (sysconfig, build-details.json etc)
    • lib-x86_64
      • x86_64 simulator-specific standard library parts (sysconfig, build-details.json etc)
    • Python.framework

• Issue: Add dylib symlink to iOS XCframework #141692

[ned-deily]

Looks to me like a good idea.

[miss-islington-app]

Thanks @freakboy3742 for the PR 🌮🎉.. I'm working now to backport this PR to: 3.14.
🐍🍒⛏🤖

[bedevere-app]

GH-141733 is a backport of this pull request to the 3.14 branch.