This package should only be built after running the 'find_aaaelflibpkgs'
script.

What's worth remembering is that Slackware's aaa_elflibs package may not
be up to date: so for example, the script may find that libusb is not
listed in the packages that comprise aaa_elflibs: yet you untar 
Slackware's and find that it is there.
This is because the script couldn't find the VERSION of libusb in aaa_elflibs
inside the MANIFEST.bz -- because aaa_elflibs has not been updated.

I could have said that in a more succint way :)