bug#41242: Port feature/native-comp to Windows

[Eli Zaretskii]

> From: Nicolas Bértolo <nicolasbertolo@gmail.com>
> Date: Thu, 14 May 2020 16:00:02 -0300
> Cc: Eli Zaretskii <eliz@gnu.org>, 41242@debbugs.gnu.org
> 
> We could use a global mutex shared between all Emacs processes.
> https://docs.microsoft.com/en-us/windows/win32/sync/mutex-objects
> 
> They would have to acquire that mutex before any operation using eln files.
> This is a complicated solution, though.

If we want a mutex, we can use the offending .eln file as that mutex:
if deletion fails, the mutex is taken.