emacs: make sure native compilation output dir is in $out (#342212)

pkgs/applications/editors/emacs/build-support/generic.nix

···
       | xargs --verbose -0 -I {} -n 1 -P $NIX_BUILD_CORES sh -c \
           "emacs \
              --batch \
+             --eval '(setq native-comp-eln-load-path (cdr native-comp-eln-load-path))' \
              --eval '(setq large-file-warning-threshold nil)' \
              --eval '(setq byte-compile-error-on-warn ${if finalAttrs.turnCompilationWarningToError then "t" else "nil"})' \
              -f batch-native-compile {} \

pkgs/applications/editors/emacs/elisp-packages/lib-override-helper.nix

···
         broken = true;
       };
     });
+
+  mkHome =
+    pkg:
+    pkg.overrideAttrs (previousAttrs: {
+      preInstall =
+        ''
+          HOME=$(mktemp -d)
+        ''
+        + previousAttrs.preInstall or "";
+    });
 }