slackbuilds_ponce/development/boost

Boost provides free peer-reviewed portable C++ source libraries. 
The emphasis is on libraries that work well with the C++ Standard 
Library. One goal is to establish "existing practice" and provide 
reference implementations so that the Boost libraries are suitable 
for eventual standardization.

If you want to build with icu4c support, than you'll need
to pass ICU="YES" to the build-script.