I tried the second solution too...
Still got this.
D:\Teste\teste\main.o:main.cpp|| undefined reference to `sf::Clock::Clock()'|
D:\Teste\teste\main.o:main.cpp|| undefined reference to `sf::Clock::GetElapsedTime() const'|
D:\Teste\teste\main.o:main.cpp|| undefined reference to `sf::Sleep(float)'|
D:\Teste\teste\main.o:main.cpp|| undefined reference to `sf::Clock::GetElapsedTime() const'|
||=== Build finished: 4 errors, 0 warnings ===|
trying to build the clock example..