title: How to know library variable names for CMakeLists?
body: <p>When using CMakeLists to compile an OpenGL project, I have the following line to link glut and gl:</p>
  
  <pre><code>target_link_libraries(my_exe ${OPENGL_gl_LIBRARY} ${GLUT_LIBRARIES})
  </code></pre>
  
  <p>I looked up how to link glut and gl with CMake so I saw that I could use ${OPENGL_gl_LIBRARY} and ${GLUT_LIBRARIES}. But how would I know the variables to use otherwise? I am used to just doing ${THELIBRARY_LIBRARES}, but in the case of gl, it changed to adding that "<em>gl</em>" into the variable name. How would I know that without googling it (for any library I want to use)?</p>