title: CMake find_package can't find my MinGW libjpeg
body: <p>I get the error : Could NOT find JPEG (missing: JPEG_LIBRARY JPEG_INCLUDE_DIR)
  when using </p>
  
  <pre><code>FIND_PACKAGE(JPEG REQUIRED)
  IF(JPEG_FOUND)
    INCLUDE_DIRECTORIES(${JPEG_INCLUDE_DIR})
    TARGET_LINK_LIBRARIES(mpo ${JPEG_LIBRARIES})
  ENDIF()
  </code></pre>
  
  <p>I have libjpeg installed under </p>
  
  <pre><code>C:\MinGW\
      |-lib\       for libjpeg.a
      |-include\   for jpeglib.h
  </code></pre>
  
  <p>Is there anything I missed ?
  I'm using the <strong>MSYS Makefiles</strong> generator</p>