bug#74382: `compile-first` Make rule is no longer using `load-prefer-newer`

[Konstantin Kharlamov <Hi-Angel@yandex.ru>]

On Sun, 2024-11-17 at 17:53 +0200, Eli Zaretskii wrote:
> > From: Konstantin Kharlamov <Hi-Angel@yandex.ru>
> > Cc: gerd.moellmann@gmail.com, acm@muc.de, 74382@debbugs.gnu.org
> > Date: Sun, 17 Nov 2024 18:43:17 +0300
> > 
> > On Sun, 2024-11-17 at 17:37 +0200, Eli Zaretskii wrote:
> > > > Cc: Alan Mackenzie <acm@muc.de>, 74382@debbugs.gnu.org
> > > > From: Konstantin Kharlamov <Hi-Angel@yandex.ru>
> > > > Date: Sun, 17 Nov 2024 18:21:36 +0300
> > > > 
> > > > On Sun, 2024-11-17 at 08:25 +0100, Gerd Möllmann wrote:
> > > > > Konstantin Kharlamov <Hi-Angel@yandex.ru> writes:
> > > > > 
> > > > > > Sure, I just reproduced it after removing all `.elc` files
> > > > > > in
> > > > > > the
> > > > > > repo,
> > > > > > here how:
> > > > > > 
> > > > > > 1. `git checkout f2f13fa630b` (a commit from April)
> > > > > > 2. `make -j$(nproc)` to compile. Note: you don't need to
> > > > > > wait
> > > > > > for
> > > > > > build
> > > > > > to finish, I just waited for all files under `lisp/emacs-
> > > > > > lisp`
> > > > > > directory to finish compilation, and then ^C'ed it.
> > > > > > 3. `git checkout 29098a291f5` (a November commit).
> > > > > > 4. `make -j$(nproc)`
> > > > > 
> > > > > This would always work if lisp/Makefile would rm the .elc
> > > > > files
> > > > > from
> > > > > COMPILE_FIRST, right? I suspect this isn't done to speed up
> > > > > the
> > > > > build
> > > > > in
> > > > > the usual case, and because it's a bit difficult to
> > > > > automatically
> > > > > determine if it has to done or not.
> > > > > 
> > > > > Does a "make clean" after the checkout in (3) make it work?
> > > > 
> > > > I don't think so, because `make clean` for some reason doesn't
> > > > remove
> > > > `.elc` artifacts.
> > > 
> > > And it shouldn't, because *.elc files are part of a release
> > > tarball.
> > 
> > But if someone decided to build from a release tarball, sure they
> > can
> > produce .elc files as well, can't they?
> 
> No, Emacs release tarballs come with *.elc files, and users shouldn't
> recompile them.  For starters, it makes the build significantly
> longer, besides being unnecessary.
> 
> Recompiling *.elc files is only needed if the corresponding *.el
> files
> are modified, something that doesn't normally happen when you build a
> release tarball.

Okay. So, how about a compromise here: provide release tarball with
modified Makefiles which upon calling `make clean` would not remove
`.elc` files — but let `make clean` inside git-repository remove elc
files?

Users expect `make clean` to remove non-config-related bulid artifacts.
Which includes `.elc` files. I can't count how many times I was
forgetting about this peculiarity of Emacs build system, and after
finding out that even `make clean` doesn't help with build errors (due
to COMPILE_FIRST files stuff), I had to nuke everything with `git clean
-fdx`. Even Gerd in this discussion forgot about this peculiarity — and
Gerd unlike me is a regular Emacs developer.