If you are having linking issues with building QT on Gentoo [similar to filexyz.o can not link] don’t forget to remove references to pipe in the CXXFLAGS, and the multiple processor arguments on the OPTIONS flag. (-j3 etc).
If you are having issues with getting KDE to recognize the battery status, or react to any hardware, check your D-BUS and HAL configuraiton. Make sure the services are started and added to boot time.