/home/yuki/projects/testas/build> make
-- Configuring done
-- Generating done
-- Build files have been written to: /home/yuki/projects/testas/build
Scanning dependencies of target testas
Linking CXX executable testas
/home/yuki/projects/testas/main.cpp:7: error: undefined reference to 'glClearColor'
/home/yuki/projects/testas/main.cpp:8: error: undefined reference to 'glClear'
/home/yuki/projects/testas/main.cpp:10: error: undefined reference to 'glFlush'
collect2: ld returned 1 exit status
make[2]: *** [testas] Error 1
make[1]: *** [CMakeFiles/testas.dir/all] Error 2
make: *** [all] Error 2
*** Failed ***