title: CMake: can't find header files
body: <p>I have a directory main, which has the following subdirectories:
  A, B, C, D, Test.</p>
  
  <p>In Test, I have a CMakeLists file with the following content:</p>
  
  <pre><code>cmake_minimum_required(VERSION 2.8)
  enable_testing()
  set(TEST_EXE_NAME test)
  add_executable(${TEST_EXE_NAME} test.cpp)
  add_test(NAME "testDatabase" COMMAND ${TEST_EXE_NAME})
  target_include_directories(Test PUBLIC ./)
  target_include_directories(Test A B C D)
  target_link_libraries(Test A B C D)
  </code></pre>
  
  <p>In Test, I have an executable which #includes several header files from A, B, C, and D.</p>
  
  <p>However, after doing make, I get the message that cmake cannot find these header files from A, B, C, and D. </p>
  
  <p>How can I make this go away?</p>