LLDB CMake: add option to link Swift content from Darwin toolchain

[edymtt]

This is a companion to apple/swift#73255, and it's needed in some Apple internal configurations.

Addresses rdar://127113448

[edymtt]

@swift-ci Please test

[edymtt]

@swift-ci test llvm

[edymtt]

The failure for "LLVM Test Linux Platform" and "Swift Test Linux Platform" is unrelated to this PR, since it happened also in another run for a different PR

/home/build-user/llvm-project/llvm/lib/MCCAS/MCCASObjectV1.cpp:2693:53: error: 'CompressedBuff' was not declared in this scope

Similarly, "LLVM Test macOS Platorm" fails the same was at the previous PR (according to the matching run)

Failed Tests (3):
  Clang :: CodeGen/ptrauth-debuginfo.c
  Clang :: CodeGenCXX/ptrauth-member-function-pointer.cpp
  Clang :: CodeGenCXX/ptrauth-virtual-function.cpp

The failure for "Swift Test macOS Platform" looks to be unrelated to this change (which affects LLDB and is inert by default)

/Users/ec2-user/jenkins/workspace/apple-llvm-project-pr-macos/branch-next/swift/include/swift/Basic/StableHasher.h:136:29: error: no member named 'endianness' in namespace 'llvm::support'; did you mean 'llvm::endianness'?
    constexpr auto endian = llvm::support::endianness::little;
                            ^~~~~~~~~~~~~~~~~~~~~~~~~
                            llvm::endianness

Same for "Swift Test Windows Platform"

C:\Users\swift-ci\jenkins\workspace\apple-llvm-project-pull-request-windows\swift\include\swift/Localization/LocalizationFormat.h(80): error C2065: 'little': undeclared identifier

[edymtt]

To get more meaningful signal, cherry-picking preemptively this PR swift/release/6.0 and running testing there.

[edymtt]

The matching 6.0 PR has run Swift PR testing successfully.