bug#36649: 27.0.50; pure space and pdumper

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: Eli Zaretskii <eliz@gnu.org>,  pipcet@gmail.com,  36649@debbugs.gnu.org,
>   monnier@iro.umontreal.ca
> Date: Sat, 02 Jul 2022 14:41:01 +0200
> 
> > unexec isn't doing any harm by itself, so there's no reason to not keep
> > it.  I don't forsee much trouble in keeping pure space behind a few
> > ifdefs; it should be a mostly mechanical job.
> 
> But Eli doesn't want to get rid of purespace (which we do want to) until
> we get rid of unexec, so unexec is blocking progress in that sense.

No, I'm okay with having the purespace removed from the pdumper
builds, if the unexec build can still use it.  AFAIU, that's the
"behind several ifdefs" alternative.