Skip code signing for the Darwin Nix package

nix/desktop-package.nix

@@ -117,6 +117,8 @@ buildNpmPackage {
       chmod -R u+w "$electron_dist/Electron.app"
       (
         cd packages/desktop
+        # The Nix output is not a distributable DMG, so leave it unsigned and
+        # disable the hardened runtime that requires a matching signature.
         CSC_IDENTITY_AUTO_DISCOVERY=false \
           ../../node_modules/.bin/electron-builder \
             --config electron-builder.yml \
@@ -124,6 +126,8 @@ buildNpmPackage {
             --mac \
             --publish never \
             --config.electronDist="$electron_dist" \
+            --config.mac.identity=null \
+            --config.mac.hardenedRuntime=false \
             --config.mac.notarize=false
       )
     ''}