replace makeSearchPath tree-wise to take care of possible multiple outputs

nixos/modules/system/boot/loader/grub/grub.nix

@@ -55,10 +55,10 @@ let
         version extraConfig extraPerEntryConfig extraEntries
         extraEntriesBeforeNixOS extraPrepareConfig configurationLimit copyKernels timeout
         default fsIdentifier efiSupport gfxmodeEfi gfxmodeBios;
-      path = (makeSearchPath "bin" ([
+      path = (makeBinPath ([
         pkgs.coreutils pkgs.gnused pkgs.gnugrep pkgs.findutils pkgs.diffutils pkgs.btrfs-progs
         pkgs.utillinux ] ++ (if cfg.efiSupport && (cfg.version == 2) then [pkgs.efibootmgr ] else [])
-      )) + ":" + (makeSearchPath "sbin" [
+      )) + ":" + (makeSearchPathOutputs "sbin" ["bin"] [
         pkgs.mdadm pkgs.utillinux
       ]);
     });

nixos/modules/system/boot/systemd-unit-options.nix

@@ -193,7 +193,7 @@ in rec {
 
     path = mkOption {
       default = [];
-      apply = ps: "${makeSearchPath "bin" ps}:${makeSearchPath "sbin" ps}";
+      apply = ps: "${makeBinPath ps}:${makeSearchPathOutputs "sbin" ["bin"] ps}";
       description = ''
         Packages added to the service's <envar>PATH</envar>
         environment variable.  Both the <filename>bin</filename>