You can change the "s,x,x" part adding --transform command line option
to configure. It's useful to change all the pathes used.
The problem is that slackware and other distributions use a "*.new"
renaming pattern when upgrading packages, in order to not overwrite
important config files. Then the user has to deal with these .new
files, rename, overwrite or toss away.
If 'grub-mkconfig' is really doing what I think it does, then it would
just overwrite this important file, '/boot/grub/grub.cfg.new'.
grub.cfg shouldn't be packaged at all. It's autogenerated on the target
system.