bug#48117: 28.0.50; Update of loaddefs.el during normal build is unreliable

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: Glenn Morris <rgm@gnu.org>,  48117@debbugs.gnu.org
> Date: Sun, 02 May 2021 09:28:04 +0200
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >> 1) autoload generation is slow.
> >
> > Based on my latest experience, I think this is somewhat exaggerated,
> > especially given that our builds became slower lately.
> 
> Has it?  I haven't noticed any substantial slow-down...  (Unless you
> mean with native-comp switched on.)

Yes, native-comp, certainly.  But the build became slower a year or so
ago as well, I no longer remember why.

> In any case, autoload generation takes a substantial chunk of time --
> especially since it's single-threaded.  Glenn's suggestion to copy over
> ldefs-boot.el (if it's newer) sounds like a good idea to me.

Yes, I agree.