anchor.diff:  { lib, stdenv, llvm_meta, cmake, python3, fetch, libcxx, libunwind, llvm, version
   , enableShared ? !stdenv.hostPlatform.isStatic
  +, standalone ? stdenv.hostPlatform.useLLVM or false
  +, withLibunwind ? !stdenv.isDarwin && !stdenv.isFreeBSD && !stdenv.hostPlatform.isWasm
   }:
   
   stdenv.mkDerivation {
  
positive.code:         # the magic combination of necessary CMake variables
          # if you fancy a try, take a look at
          # https://gitlab.kitware.com/cmake/community/-/wikis/doc/cmake/RPATH-handling
          install_name_tool -id $out/$file $file
        done
        make install
        install -d 755 $out/include
  
negative.code:   ];
  
    nativeBuildInputs = [ cmake python3 ];
    buildInputs = lib.optional withLibunwind libunwind;
  
    cmakeFlags = lib.optionals standalone [
      "-DLLVM_ENABLE_LIBCXX=ON"
      "-DLIBCXXABI_USE_LLVM_UNWINDER=ON"
    ] ++ lib.optionals stdenv.hostPlatform.isWasm [
  