title: CMake cannot determine linker language for target
body: <p>To start off, I've taken a look at <a href="https://stackoverflow.com/questions/11801186/cmake-unable-to-determine-linker-language-with-c">this</a> post and couldn't find a solution to my problem. I'm attempting to set up a library in a folder using two header files and link with my main program, in my folder <em>container</em> it includes:</p>
  
  <pre><code>linkedStack.h
  linkedQueue.h
  </code></pre>
  
  <p>the CMakeLists.txt in my container folder is</p>
  
  <pre><code>add_library(container linkedQueue.h linkedStack.h)
  
  install (TARGETS container DESTINATION bin)
  install (FILES linkedQueue.h linkedStack.h DESTINATION include)
  </code></pre>
  
  <p>while my CMakeLists.txt in the source directory is:</p>
  
  <pre><code>cmake_minimum_required(VERSION 2.6)
  project(wordLadder)
  
  # set version number
  set (MAJOR 1)
  set (MINOR 0)
  
  # configure header file to be placed in binary
  configure_file(
          "${PROJECT_SOURCE_DIR}/ladderConfig.h.in"
          "${PROJECT_BINARY_DIR}/ladderConfig.h"
  )
  
  # add binary tree to search path for include files
  # so we can find config
  include_directories("${PROJECT_BINARY_DIR}")
  
  #add container library
  include_directories ("${PROJECT_SOURCE_DIR}/container")
  add_subdirectory(container)
  
  #add executable
  add_executable(wordLadder ladderMain.cpp)
  target_link_libraries (wordLadder container)
  
  install (TARGETS wordLadder DESTINATION bin)
  install (FILES "${PROJECT_BINARY_DIR}/ladderConfig.h"
           DESTINATION include)
  </code></pre>
  
  <p>and the error I get:</p>
  
  <pre><code>CMake Error: Cannot determine link language for target "container".
  CMake Error: CMake can not determine linker language for target:container
  -- Generating done
  -- Build files have been written to: /home/gmercer/Linux_dev/wordLadder/build
  </code></pre>
  
  <p>I'm not sure what i'm doing wrong here, but I think it has something to do with my library CMake file.</p>