bug#61960: 30.0.50; Unexec build reliably crashes during loadup

[Konstantin Kharlamov]

So, just to add some points: apparently it isn't so easy to reproduce. I built 
Emacs with unexec without first looking at the `./configure` line in the report 
(looking at the report I apparently lack the `with-dumping=unexec`), and 
removed the workaround to not have BLOCK_SIZE=2¹⁵ if HAVE_UNEXEC. (worth noting 
probably that I first did the build, then remembered I had to remove the work 
around installed on master branch, then re-built emacs without the workaround).

Running `emacs` as well as running the `temacs` command ain't shows no crashes.

My configuration was: --prefix=/usr --sysconfdir=/etc --libexecdir=/usr/lib 
--localstatedir=/var --mandir=/usr/share/man --with-gameuser=:games 
--with-modules --without-libotf --without-m17n-flt --without-gconf 
--enable-link-time-optimization --with-native-compilation=yes --with-xinput2 
--with-x-toolkit=gtk3 --without-xaw3d --with-sound=no --with-tree-sitter 
--without-gpm --without-compress-install 
'--program-transform-name=s/\\([ec]tags\\)/\\1.emacs/' 'CFLAGS=-flto=2 
-march=native -O3 -pipe -fno-stack-protector -fweb -fmerge-all-constants 
-fno-plt -fcommon' 'LDFLAGS=-flto=2 -O3 -march=native -fweb 
-fmerge-all-constants -floop-nest-optimize -Wl,--sort-common,-z,relro -fno-plt 
-fcommon'

I will try to reconfigure build with the flags Eli reports. I seems to have 
lacked `with-dumping=unexec` option, but I'll try running `configure` only with 
the flags mentioned, just for the safe case.