libsysstat is a library to query system information like CPU and memory usage or network traffic. Conceptually it's roughly similar to libstatgrab, a third-party library used by LXQt as well.
It is maintained by the LXQt project but can be used independently from this desktop environment, too. As for LXQt libsysstat is used by plugin-sysstat of lxqt-panel and hence an optional dependency of the latter.
Note replacing both libsysstat and libstatgrab in LXQt by KDE Frameworks components is being considered but a final decision hasn't been made yet, see https://github.com/lxde/lxqt/issues/704.
The only runtime dependency is qtbase. To build CMake and lxqt-build-tools are needed in addition, as well as optionally Git to pull latest VCS checkouts.
Code configuration is handled by CMake. CMake variable
CMAKE_INSTALL_PREFIX will normally have to be set to
/usr, depending on the way library paths are dealt with on 64bit systems variables like
CMAKE_INSTALL_LIBDIR may have to be set as well.
To build run
make, to install
make install which accepts variable
DESTDIR as usual.
The library is provided by all major Linux distributions like Arch Linux, Debian, Fedora and openSUSE.
Just use the distributions' package managers to search for string