use-qt5xdgiconloader-target-alone

CMakeLists.txt

project(iconloader)
cmake_minimum_required(VERSION 3.0.2 FATAL_ERROR)

find_package(Qt5Xdg REQUIRED)

# This one should be included in the Qt5XdgIconLoader Target
include_directories(${Qt5Gui_PRIVATE_INCLUDE_DIRS})

add_executable(iconloader main.cpp)
target_link_libraries(iconloader Qt5XdgIconLoader)

main.cpp

#include <private/xdgiconloader/xdgiconloader_p.h>
#include <QGuiApplication>
#include <QDebug>

int main(int argc, char *argv[])
{
    QGuiApplication a(argc, argv);
    qDebug() << XdgIconLoader::instance()->themeName();
    return 0;

}