Pacbuilder is a small but powerful script to automatically recompile the whole system, repos or just a single package (with or without its dependencies). This is quite useful once you have edited /etc/makepkg.conf with some customized CFLAGS.
To see actual CFLAGS and CXXFLAGS run:
Most used command:
pacbuilder --builddeps --keepdeps --verbose --noconfirm --install $packagename
pacbuilder -Sbkvn $packagename
pacbuilder -h to show a list of all options along with a description.