bug#57878: Emacs native compilation on startup can crash the system

[Konrad Hinsen <konrad.hinsen@fastmail.net>]

After updating to a commit after the introduction of native compilation
in Emacs, I cannot start Emacs any more. It launches an ever increasing
number of async processes for native compilation, which rapidly makes
kswapd the main CPU user on my machine, and ultimately crashes the
kernel.

Some experiments showed that it's loading the site-lisp/site-start.el  that
causes this avalanche of processes:

  emacs -Q --batch --eval="(print load-path)"

works fine. As does:

  emacs -Q --batch --load=~/.guix-profile/share/emacs/site-lisp/guix-emacs.el --eval="(print load-path)"

But not:

  emacs -Q --batch --load=~/.guix-profile/share/emacs/site-lisp/site-start.el --eval="(print load-path)"

which starts the avalanche of compilation.

Possibly related: in my user-dir (~/.emacs.d/) I have a directory
"eln-cache" containing a directory "28.1-f1a30909", but that directory
remains empty. Perhaps all native compilation attempts fail and that's
what causes the problem. Just guessing!

Cheers,
  Konrad.