anchor.diff:    '' + lib.optionalString stdenv.hostPlatform.isMusl ''
       patch -p1 -d $(ls -d libcxx-*) -i ${../../libcxx-0001-musl-hacks.patch}
     '';
  -
  -  cmakeFlags = lib.optionals standalone [
  -    "-DLLVM_ENABLE_LIBCXX=ON"
  -    "-DLIBCXXABI_USE_LLVM_UNWINDER=ON"
  -  ] ++ lib.optional (!enableShared) "-DLIBCXXABI_ENABLE_SHARED=OFF";
   
     installPhase = if stdenv.isDarwin
       then ''
  
positive.code: { lib, stdenv, cmake, fetch, libcxx, libunwind, llvm, version
  , standalone ? stdenv.hostPlatform.useLLVM or false
    # on musl the shared objects don't build
  , enableShared ? !stdenv.hostPlatform.isStatic
  }:
  
negative.code:   src = fetch "libcxxabi" "1zcqxsdjhawgz1cvpk07y3jl6fg9p3ay4nl69zsirqb2ghgyhhb2";
  
    nativeBuildInputs = [ cmake ];
    buildInputs = lib.optional withLibunwind libunwind;
  
    cmakeFlags = lib.optionals standalone [
      "-DLLVM_ENABLE_LIBCXX=ON"
    ] ++ lib.optionals (standalone && withLibunwind) [
      "-DLIBCXXABI_USE_LLVM_UNWINDER=ON"
    ] ++ lib.optional (!enableShared) "-DLIBCXXABI_ENABLE_SHARED=OFF";
  
    postUnpack = ''
      unpackFile ${libcxx.src}
  