This patch switches the CoreFoundation on x86_64-darwin from the open
source swift-corelibs-foundation (CF) to the system CoreFoundation.

This change was motivated by failures building packages for the current
staging-next cycle NixOS#263535 due to an apparent incompatibility with the
rpath-based approach to choosing CF or CoreFoundation and macOS 14. This
error often manifests as a crash with an Illegal Instruction.

For example, building aws-sdk-cpp for building Nix will fail this way.

https://hydra.nixos.org/build/239459417/nixlog/1

    Application Specific Information:
    CF objects must have a non-zero isa

    Error Formulating Crash Report:
    PC register does not match crashing frame (0x0 vs 0x7FF8094DD640)

    Thread 0 Crashed::  Dispatch queue: com.apple.main-thread
    0   CoreFoundation                	    0x7ff8094dd640 CF_IS_OBJC.cold.1 + 14
    1   CoreFoundation                	    0x7ff8094501d0 CF_IS_OBJC + 60
    2   CoreFoundation                	    0x7ff8093155e8 CFRelease + 40
    3   ???                           	       0x10c7a2c61 s_aws_secure_transport_ctx_destroy + 65
    4   ???                           	       0x10c87ba32 aws_ref_count_release + 34
    5   ???                           	       0x10c7b7adb aws_tls_connection_options_clean_up + 27
    6   ???                           	       0x10c596db4 Aws::Crt::Io::TlsConnectionOptions::~TlsConnectionOptions() + 20
    7   ???                           	       0x10c2d249c Aws::CleanupCrt() + 92
    8   ???                           	       0x10c2d1ff0 Aws::ShutdownAPI(Aws::SDKOptions const&) + 64
    9   ???                           	       0x102d9bc6f main + 335
    10  dyld                          	       0x202f333a6 start + 1942

According to a [post][1] on the Apple developer forums, hardening was
added to CoreFoundation, and this particular message occurs when you
attempt to release an object it does not recognize as a valid CF object.
(Thank you to @lilyinstarlight for finding this post).

When I switched aws-sdk-cpp to link against CoreFoundation instead of
CF, the error went away. Somehow both libraries were being used. To
prevent dependent packages from linking the wrong CoreFoundation, it
would need to be added as a propagated build input.

Note that there are other issues related to mixing CF and CoreFoundation
frameworks. NixOS#264503 fixes an issue with abseil-cpp where it propagates
CF, causing issues when using a different SDK version. Mixing versions
can also cause crashes with Python when a shared object is loaded that
is linked to the “wrong” CoreFoundation.

`NIX_COREFOUNDATION_RPATH` is supposed to make sure the right
CoreFoundation is being used, but it does not appear to be enough on
macOS 14 (presumably due to the hardening). While it is possible to
propagate CoreFoundation manually, the cleaner solution is to make it
the default. CF remains available as `darwin.swift-corelibs-foundation`.

[1]: https://developer.apple.com/forums/thread/739355