bug#53678: 29.0.50; Invalid read syntax: "#<" for package install in Windows

[Shuguang Sun]

Hi,

When I try to install packages from the Package Menu or the command of
package-install since about two weeks ago, it reports the error:
```
error in process sentinel: async-when-done: Invalid read syntax: "#<"
error in process sentinel: Invalid read syntax: "#<"
```
And it seems not preventing the installation process but stops the emacs
to compile the el files to elc.

FYI. I failed to find out what makes it. It looks like the local variable in
the autoloads file generated by the package process. It add
`;; coding: utf-8-emacs-unix`, however, in windows, the file is probablly
in a coding of utf-8-emacs-dos. When I try to open the autoload file,
Emacs can't regonize the major mode which assumes to be `emacs-lisp-mode`.
Unless I change the `;; coding: utf-8-emacs-unix` to
`;; coding: utf-8-emacs`, it can be open in the `emacs-lisp-mode`.



Best Regards,
Shuguang Sun

In GNU Emacs 29.0.50 (build 1, x86_64-w64-mingw32)
 of 2022-01-31 built on YJ190169-SSG
Repository revision: 04f9c3b8df6afaf1e9de9f2a4478f63fd959bf09
Repository branch: master
Windowing system distributor 'Microsoft Corp.', version 10.0.19044
System Description: Microsoft Windows 10 Pro (v10.0.2009.19044.1466)

Configured using:
 'configure --without-pop --with-native-image-api
 --with-native-compilation --without-compress-install
 '--program-transform-name=s/^ctags$/ctags.emacs/''

Configured features:
ACL DBUS GIF GMP GNUTLS HARFBUZZ JPEG JSON LCMS2 LIBXML2 MODULES
NATIVE_COMP NOTIFY W32NOTIFY PDUMPER PNG RSVG SOUND SQLITE3 THREADS TIFF
TOOLKIT_SCROLL_BARS WEBP XPM ZLIB

Important settings:
  value of $LANG: CHS
  locale-coding-system: cp936