Xcode 15 Beta Swift/C++ Interop with C++20

I have a C++ project that produces a lot of libraries that require C++20.

I have tried to set the requirement for that in the module.modulemap like so (for example):

module cxx_library {
  requires cplusplus20
  header "library.h"
  link "CXXLibrary"
}

This seems to be correct per the clang documentation: https://clang.llvm.org/docs/Modules.html#requires-declaration

However I cannot figure out how to get cmd+click on the imported module in my sample swift file to work with this. For one, Xcode seems to refuse to even import my module when it requires C++20.

How do I tell Xcode that all of my C++/ObjectiveC++ requires C++20? The compiler default is C++14, but it's not clear how to properly change that so that I can import a C++20-enabled clang module into some sample swift projects to try out the new interior features.

If I remove the 20 from my requires statement, and just use my code as-is, It always complains in the UI that:

Couldn't Generate Swift Representation

Error (from SourceKit): "Could not load module: cxx_library (could not build Objective-C module 'cxx_library', unknown type name 'char8_t')"

Which is very frustrating. When I compile with CMake, I can just set this:

add_executable(E
  E.swift)
target_compile_options(E PRIVATE
  -cxx-interoperability-mode=default
  SHELL:-Xcc SHELL:-std=c++20)
target_link_libraries(E PRIVATE
  cxx_library)

And swiftc compiles the code with no issue.

I have uploaded a minimized version of my code as a fork of a project by compnerd on GitHub here: https://github.com/ADKaster/swift-cmake-examples/tree/main/Interop

The project builds just fine with

cmake -S Interop -B build -GNinja
cmake --build build

But by creating an Xcode project from it:

cmake -S Interop -B build-xcode -GXcode

and then opening build-xcode/P.xcodeproj in Xcode 15 Beta, and trying to cmd-click on import cxx_library in E.swift does not work.