make-desktopitem: desktop-file-utils is a nativeBuildInput

This fixes cross-compilation of a NixOS with the manual enabled.

pkgs/build-support/make-desktopitem/default.nix

@@ -16,10 +16,10 @@
 , extraEntries ? "" # Extra configuration. Will be appended to the end of the file and may thus contain extra sections
 , fileValidation ? true # whether to validate resulting desktop file.
 }:
-
 let
   # like builtins.toString, but null -> null instead of null -> ""
-  nullableToString = value: if value == null then null
+  nullableToString = value:
+    if value == null then null
     else if builtins.isBool value then lib.boolToString value
     else builtins.toString value;
 
@@ -48,7 +48,10 @@ let
       )
     ++ (if extraEntries == "" then [ ] else [ "${extraEntries}" ]);
 in
-runCommandLocal "${name}.desktop" {}
+runCommandLocal "${name}.desktop"
+{
+  nativeBuildInputs = [ desktop-file-utils ];
+}
   (''
     mkdir -p "$out/share/applications"
     cat > "$out/share/applications/${name}.desktop" <<EOF
@@ -56,5 +59,5 @@ runCommandLocal "${name}.desktop" {}
     EOF
   '' + lib.optionalString fileValidation ''
     echo "Running desktop-file validation"
-    ${desktop-file-utils}/bin/desktop-file-validate "$out/share/applications/${name}.desktop"
+    desktop-file-validate "$out/share/applications/${name}.desktop"
   '')