outputs.zimage -> outputs.kernel.zImage

remove config option/derivation in favour of accessing
as output of the kernel derivation (matches what we do
with e.g. modulesupport)

modules/kernel/default.nix

@@ -68,19 +68,15 @@ in {
     };
   };
   config = {
-    system.outputs =
+    system.outputs.kernel =
       let
         mergedConfig = mergeConditionals
           config.kernel.config
           config.kernel.conditionalConfig;
-        k = liminix.builders.kernel.override {
-          config = mergedConfig;
-          inherit (config.kernel) version src extraPatchPhase;
-          targets = config.kernel.makeTargets;
-        };
-      in {
-        kernel = k.vmlinux;
-        zimage = k.zImage;
+      in liminix.builders.kernel.override {
+        config = mergedConfig;
+        inherit (config.kernel) version src extraPatchPhase;
+        targets = config.kernel.makeTargets;
       };
 
     kernel = rec {

modules/outputs.nix

@@ -28,17 +28,7 @@ in
           kernel
           ******
 
-          Kernel vmlinux file (usually ELF)
-        '';
-      };
-      zimage = mkOption {
-        type = types.package;
-        internal = true;
-        description = ''
-          zimage
-          ******
-
-          Kernel in compressed self-extracting package
+          Kernel package (multi-output derivation)
         '';
       };
       dtb = mkOption {

modules/outputs/extlinux.nix

@@ -24,7 +24,7 @@ in {
       cd $out
       ${if wantsDtb then "cp ${o.dtb} dtb" else "true"}
       cp ${o.initramfs} initramfs
-      cp ${o.zimage} kernel
+      cp ${o.kernel.zImage} kernel
       mkdir extlinux
       cat > extlinux/extlinux.conf << _EOF
       menu title Liminix

modules/outputs/tftpboot.nix

@@ -61,7 +61,7 @@ in {
           o = config.system.outputs;
           image = let choices = {
             uimage = o.uimage;
-            zimage = o.zimage;
+            zimage = o.kernel.zImage;
           }; in choices.${cfg.kernelFormat};
           bootCommand = let choices = {
             uimage = "bootm";