Yes, I have been in touch with the developer of i3 who also maintains a Debian i3 package. I haven't finished it yet but following Michael's comments I've cleaned it a bit removing unnecessary bits:
# instead of ./configure
sed -i "s,local/lib,lib$LIBDIRSUFFIX," common.mk
The only references to "local/lib" in common.mk only applied to NetBSD.
# make building verbose
sed -i "/^\.SILENT/d" common.mk
was replaced with:
I also liked how ponce organised docs - so I pinched it from his script (Thank you
Now the reason his script worked for you is because it didn't try to compile man pages (just copied pre-delivered ones - nothing wrong with it).
My script attempts to compile the man pages and that's where it failed for you. Michael, i3 developer, said that he'd seen that error before and:
I think xmlto is not installed or
something else is wrong with the asciidoc setup.
I think it might be the case as I tried my script on 2 clean FULL -current installs and it built without any problems. I think most (all?) Slackware package maintainers prepare scripts for FULL Slackware installs.