yea, i noticed that as well. Not sure what do, I will likely disable darwin platform.

it happens because unicode filenames yield a different hash on darwin NixOS/nix#847
I think you can either:

1. Specify the other hash for darwin:

   --- c/pkgs/development/libraries/onnxruntime/default.nix
   +++ i/pkgs/development/libraries/onnxruntime/default.nix
   @@ -10,7 +10,10 @@ stdenv.mkDerivation rec {
        owner = "microsoft";
        repo = "onnxruntime";
        rev = "v${version}";
   -    sha256 = "03c5h5pp67a51blc26kw08piax81116jp7l2illzrsnx0580m6ri";
   +    sha256 =
   +      if stdenv.isDarwin
   +      then "…"
   +      else "…";
        # TODO: use nix-versions of grpc, onnx, eigen, googletest, etc.
        # submodules increase src size and compile times significantly
        # not currently feasible due to how integrated cmake build is with git

2. Remove the offending files, so fetchFromGitHub yields the same hash:

   --- c/pkgs/development/libraries/onnxruntime/default.nix
   +++ i/pkgs/development/libraries/onnxruntime/default.nix
   @@ -15,6 +15,11 @@ stdenv.mkDerivation rec {
        # submodules increase src size and compile times significantly
        # not currently feasible due to how integrated cmake build is with git
        fetchSubmodules = true;
   +    # Remove unicode file names which leads to different checksums on HFS+
   +    # vs. other filesystems because of unicode normalisation.
   +    postFetch = ''
   +      rm -rf winml/test/collateral/models/UnicodePath/
   +    '';
      };
   
      # TODO: build server, and move .so's to lib output

@GrahamcOfBorg build onnxruntime

Since ofborg build timed out: building on my MacBook now.