Cmake error while trying to install sbopkg

About a week ago I installed slackware64 xfce stable and am attempting my first install from slackbuilds (the app is sbopkg), but the machine keeps failing and I have no idea how to fix the problem.

The install quits at

Code:-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Found Curses: /usr/lib64/libcurses.so
CMake Error at cmake/Modules/FindLibconfig++.cmake:13 (message):
Could NOT find libconfig++.h!
Call Stack (most recent call first):
CMakeLists.txt:70 (find_package)

-- Configuring incomplete, errors occurred!
See also "/tmp/SBo/sboui-2.1/build/CMakeFiles/CMakeOutput.log".Thinking that I could fix the problem by installing libconfig++h I went looking for it, however

Code:bash-4.3# slackpkg search libconf

Looking for libconf in package list. Please wait... DONE

No package name matches the pattern.As the machine suggests I looked at the .....CMakeOutput.log.

Nano tells me the file is 536 lines, which is too long to post here and I don't know which section to post. Nor where the error is.

Suggestions to fix this problem would be appreciated.