dotnet-sdk: add updateScript

This update script calls the existing update.sh script with the proper
arguments. If not an SDK package, run a dummy script which allows the update.nix
script to work properly.
This should allow dotnet to be update automatically.

pkgs/development/compilers/dotnet/build-dotnet.nix

@@ -23,6 +23,7 @@ assert if type == "sdk" then packages != null else true;
 , lttng-ust_2_12
 , testers
 , runCommand
+, writeShellScript
 }:
 
 let
@@ -121,6 +122,24 @@ stdenv.mkDerivation (finalAttrs: rec {
       "aarch64-darwin" = "osx-arm64";
     };
 
+    updateScript =
+      if type != "sdk" then
+        lib.warn "${pname}-${version}: only the SDK package can be updated - this script will do nothing!"
+        writeShellScript "dummy-update" ''
+          echo "Doing nothing..."
+          echo "Run the updateScript from the SDK package"
+        ''
+      else
+      let
+        majorVersion =
+          with lib;
+          concatStringsSep "." (take 2 (splitVersion version));
+      in
+      writeShellScript "update-dotnet-${majorVersion}" ''
+        pushd pkgs/development/compilers/dotnet
+        exec ${./update.sh} "${majorVersion}"
+      '';
+
     # Convert a "stdenv.hostPlatform.system" to a dotnet RID
     systemToDotnetRid = system: runtimeIdentifierMap.${system} or (throw "unsupported platform ${system}");