explicitly set macos frameworks in devenv.nix (#314)

devenv.nix

@@ -1,12 +1,15 @@
-{ pkgs, ... }:
+{ pkgs, lib, ... }:
 
 {
   # https://devenv.sh/basics/
 
   # https://devenv.sh/packages/
-  # manually set rust packages rather than use devenv language support because
-  # it doesn't seem to be up to date for macos yet (link error)
-  packages = [ ];
+  # on macos frameworks have to be explicitly specified 
+  # otherwise a linker error ocurs on rust packages
+  packages = lib.optionals pkgs.stdenv.isDarwin (with pkgs.darwin.apple_sdk; [
+    frameworks.CoreServices
+    frameworks.CoreFoundation
+  ]);
 
   # https://devenv.sh/scripts/
   scripts.hello.exec = "echo Welcome to hugr dev shell!";
@@ -19,6 +22,7 @@
   # https://devenv.sh/languages/
   # https://devenv.sh/reference/options/#languagesrustversion
   languages.rust = {
+    channel = "stable";
     enable = true;
     components = [ "rustc" "cargo" "clippy" "rustfmt" "rust-analyzer" ];
   };