title: CONAN_PKG::<PKG-NAME> not found when using cmake to generate build target
body: <p><code>CONAN_PKG::spdlog</code> is not found when using CMake to generate build configurations.</p>
  
  <p>The conan package I use is <em>spdlog/1.3.1@bincrafters/stable</em>.
  I have a CMake executable target which references a conan package <code>spdlog</code>. I am getting this error message:</p>
  
  <pre><code>[build] CMake Error at src/apps/ResultObserver/CMakeLists.txt:10 (ADD_EXECUTABLE):
  [build]   Target "ResultObserver" links to target "CONAN_PKG::spdlog" but the target
  [build]   was not found.  Perhaps a find_package() call is missing for an IMPORTED
  [build]   target, or an ALIAS target is missing?
  </code></pre>
  
  <p>I have these lines in my CMakeLists.txt.</p>
  
  <pre><code>include(${CMAKE_BINARY_DIR}/conanbuildinfo.cmake)
  conan_basic_setup()
  
  ADD_EXECUTABLE(ResultObserver src/ResultObserver.cpp)
  
  TARGET_LINK_LIBRARIES(ResultObserver CONAN_PKG::spdlog)
  </code></pre>
  
  <p>Also, after installing the conan package, the <i>conanbuildinfo.cmake</i> file is generated in the build directory.</p>
  
  <p>I checked inside the file. It contains these lines.</p>
  
  <pre><code>    add_library(CONAN_PKG::spdlog INTERFACE IMPORTED)
  
      # Property INTERFACE_LINK_FLAGS do not work, necessary to add to INTERFACE_LINK_LIBRARIES
      set_property(TARGET CONAN_PKG::spdlog PROPERTY INTERFACE_LINK_LIBRARIES .........
  </code></pre>
  
  <p>Anyone know the reason?</p>