--- !tapi-tbd
tbd-version:     4
targets:         [ x86_64-macos, x86_64-maccatalyst, arm64-macos, arm64-maccatalyst, 
                   arm64e-macos, arm64e-maccatalyst ]
install-name:    '/usr/lib/libnetwork.dylib'
reexported-libraries:
  - targets:         [ x86_64-macos, x86_64-maccatalyst, arm64-macos, arm64-maccatalyst, 
                       arm64e-macos, arm64e-maccatalyst ]
    libraries:       [ '/System/Library/Frameworks/Network.framework/Versions/A/Network' ]
...

Randy Eckenrode: this code from booter.nix seems suspicious now:

  # This is a hack for resolving cross-compiled compilers' run-time
  # deps. (That is, compilers that are themselves cross-compiled, as
  # opposed to used to cross-compile packages.)
  postStage = buildPackages: {
    __raw = true;
    stdenv.cc =
      if buildPackages.stdenv.hasCC then
        if
          buildPackages.stdenv.cc.isClang or false
        # buildPackages.clang checks targetPackages.stdenv.cc (i. e. this
        # attribute) to get a sense of the its set's default compiler and
        # chooses between libc++ and libstdc++ based on that. If we hit this
        # code here, we'll cause an infinite recursion. Since a set with
        # clang as its default compiler always means libc++, we can infer this
        # decision statically.
        then
          buildPackages.pkgsBuildTarget.llvmPackages.libcxxClang
        else
          buildPackages.gcc
      else
        # This will blow up if anything uses it, but that's OK. The `if
        # buildPackages.stdenv.cc.isClang then ... else ...` would blow up
        # everything, so we make sure to avoid that.
        buildPackages.stdenv.cc;
  };

but I guess it's only for

        else if (targetPackages.stdenv or stdenv).cc.isGNU then
          self.libstdcxxClang
        else
          self.libcxxClang;