title: How to tell CMake to link executable against library?
body: <p>My source tree is </p>
  
  <ul>
  <li>CMakeLists.txt
  
  <ul>
  <li>Demo
  
  <ul>
  <li>CMakeLists.txt</li>
  <li>source, headers.</li>
  </ul></li>
  <li>Library
  
  <ul>
  <li>CMakeLists.txt</li>
  <li>source, headers. </li>
  </ul></li>
  </ul></li>
  </ul>
  
  <p>So Demo is the executable which is done with add_executable()
  and Library is obviously the library. How can those 2 be linked together?</p>
  
  <p>Because right now I am using target_link_libraries(Demo Library) but I am getting Error: LNK2019 which I think is caused by not linking successfully. </p>
  
  <p>Any ideas?</p>
  
  <p>Thanks.</p>
  
  <p>edit: On root CMakeLists.txt those 2 are added as -> add_subdirectory(Library) add_subdirectory(Demo). </p>
  
  <p>edit2:<br>
    <strong>Demo CMakeLists</strong> </p>
  
  <pre><code>add_executable(Demo ${Headers}
                      ${Source})
  
  target_link_libraries(Demo ${blahblah}
                             ${Library})
  </code></pre>
  
  <p><strong>Library CMakeLists</strong></p>
  
  <pre><code>add_library(Library blahblah.cpp
                      blahblah.h
                      foo.cpp
                      foo.h)
  </code></pre>