emacs: remove warning of xargs when doing AOT native-comp

Before, there is a warning:

xargs: warning: options --max-args and --replace/-I/-i are mutually exclusive, ignoring previous --max-args value

According to the  manual[1], swap -I and -n can remove this warning.

[1]: https://www.gnu.org/software/findutils/manual/html_node/find_html/Conflicting-xargs-options.html

pkgs/build-support/emacs/generic.nix

@@ -85,7 +85,7 @@ stdenv.mkDerivation ({
     addEmacsVars "$out"
 
     find $out/share/emacs -type f -name '*.el' -print0 \
-      | xargs -0 -n 1 -I {} -P $NIX_BUILD_CORES sh -c \
+      | xargs -0 -I {} -n 1 -P $NIX_BUILD_CORES sh -c \
           "emacs --batch --eval '(setq large-file-warning-threshold nil)' -f batch-native-compile {} || true"
   '';
 }