move microkit platforms up so we can only have shell outputs for them…

… (remove if you want)

flake.nix

@@ -10,9 +10,16 @@
     zig-overlay.url = "github:mitchellh/zig-overlay";
   };
 
-  outputs = { self, nixpkgs, zig-overlay, ... }:
+  outputs = { nixpkgs, zig-overlay, ... }:
     let
-      forAllSystems = with nixpkgs.lib; genAttrs systems.flakeExposed;
+      microkit-version = "1.4.1";
+      microkit-platforms = {
+        aarch64-darwin = "macos-aarch64";
+        x86_64-darwin = "macos-x86-64";
+        x86_64-linux = "linux-x86-64";
+      };
+
+      forAllSystems = with nixpkgs.lib; genAttrs (builtins.attrNames microkit-platforms);
     in
     {
       # Shell for developing sDDF.
@@ -30,14 +37,9 @@
               zig = zig-overlay.packages.${system}."0.13.0";
             in
             pkgs.mkShell rec {
-              name = "dev";
+              name = "sddf-dev";
 
-              microkit-version = "1.4.1";
-              microkit-platform = {
-                aarch64-darwin = "macos-aarch64";
-                x86_64-darwin = "macos-x86-64";
-                x86_64-linux = "linux-x86-64";
-              }.${system} or (throw "Unsupported system: ${system}");
+              microkit-platform = microkit-platforms.${system} or (throw "Unsupported system: ${system}");
 
               env.MICROKIT_SDK = pkgs.fetchzip {
                 url = "https://github.com/seL4/microkit/releases/download/${microkit-version}/microkit-sdk-${microkit-version}-${microkit-platform}.tar.gz";