anchor.diff:  
     BUILD_DIR = "./Build";
     CFLAGS = "-DINCLUDE_OBJC -I${libxml2.dev}/include/libxml2"; # They seem to assume we include objc in some places and not in others, make a PR; also not sure why but libxml2 include path isn't getting picked up from buildInputs
  -  
  +
     # I'm guessing at the version here. https://github.com/apple/swift-corelibs-foundation/commit/df3ec55fe6c162d590a7653d89ad669c2b9716b1 imported "high sierra"
     # and this version is a version from there. No idea how accurate it is.
     LDFLAGS = "-current_version 1454.90.0 -compatibility_version 150.0.0 -init ___CFInitialize";
  
positive.code:     url    = "https://raw.githubusercontent.com/apple/swift-corelibs-foundation/9a5d8420f7793e63a8d5ec1ede516c4ebec939f0/CoreFoundation/Base.subproj/CFSystemDirectories.c";
      sha256 = "0krfyghj4f096arvvpf884ra5czqlmbrgf8yyc0b3avqmb613pcc";
    };
  in stdenv.mkDerivation {
    name = "swift-corefoundation";
  
    src = fetchFromGitHub {
  
negative.code:       --replace "cf.CFLAGS += '-DDEPLOYMENT" '#' \
        --replace "cf.LDFLAGS += '-ldispatch" '#'
  
      # Fix sandbox impurities.
      substituteInPlace ../lib/script.py \
        --replace '/bin/cp' cp
  
      # Includes xpc for some initialization routine that they don't define anyway, so no harm here
      substituteInPlace PlugIn.subproj/CFBundlePriv.h \
        --replace '#if (TARGET_OS_MAC' '#if (0'
  