title: Issue on using CMAKE with MSYS/MinGW linking dll files using DevIL image library
body: <p>actually i create a CMake script to localize the DevIL library using MSYS/MinGW on win32 platform. I've extend the origin FindDevIL CMake script to regard the MinGW root when try to find DevIL:</p>
  
  <pre><code>project (DevILTest)
  cmake_minimum_required(VERSION 2.6)
  
  FIND_PACKAGE(OpenGL)
  IF(OPENGL_FOUND)
    MESSAGE(STATUS "OpenGL render API found.")
    MESSAGE(STATUS "Detected OpenGL path is : ${OPENGL_LIBRARIES}")   
  ENDIF(OPENGL_FOUND)
  
  #Determine DevIL specific header file           
  FIND_PATH(IL_INCLUDE_DIR il.h 
        PATH_SUFFIXES include/IL
        PATHS c:/mingw
        DOC "The path the the directory that contains il.h"
  )
  MESSAGE("Found DevIL includes at: ${IL_INCLUDE_DIR}")
  
  #Determine DevIL library
  FIND_LIBRARY(IL_LIBRARY NAMES DEVIL
       PATH_SUFFIXES lib 
       PATHS c:/mingw
       DOC "The file that corresponds to the base il library."
  )
  MESSAGE("Found DevIL library at: ${IL_LIBRARY}")
  
  SET (Sources
  winmain.cpp
  )
  
  SET(CMAKE_VERBOSE_MAKEFILE ON)
  SET(IL_INCLUDE_DIR /c/binrev/development/mingw/include)
  
  INCLUDE_DIRECTORIES(${CMAKE_CURRENT_BINARY_DIR} 
               ${CMAKE_CURRENT_SOURCE_DIR}/src 
               ${IL_INCLUDE_DIR}
               /usr/include 
               /usr/local/include               
  )
  
  add_executable (DevILTest ${Sources})
  SET(EXECUTABLE_OUTPUT_PATH ${CMAKE_SOURCE_DIR})
  TARGET_LINK_LIBRARIES(DevILTest ${OPENGL_LIBRARIES} ${IL_LIBRARY})
  </code></pre>
  
  <p>The DevIL .dll files are placed in bin subfolder, the DevIL.lib and DevIL.a files in the lib subfolder of MinGW root (c:/mingw). I use find_library() to check if a library exists.</p>
  
  <pre><code>-- OpenGL render API found.
  -- Detected OpenGL path is : glu32;opengl32
  -- Found DevIL includes at: C:/mingw/include/IL
  -- Found DevIL library at: C:/mingw/bin/DevIL.dll
  </code></pre>
  
  <p>Find_libary() returns allways the path to the dll files - but I can't link against this library using MinGW:</p>
  
  <pre><code>Linking CXX executable DevILTest.exe
  /C/binrev/development/mingw/bin/g++.exe     "CMakeFiles/DevILTest.dir  /winmain.cpp.obj"   -o DevILTest.exe -Wl,--out-implib,libDevILTest.dll.a -Wl,--ma
  32 -lopengl32 DevIL.dll -lkernel32 -luser32 -lgdi32 -lwinspool -lshell32 -lole32 -loleaut32 -luuid -lcomdlg32 -ladvapi32
  CMakeFiles/DevILTest.dir/winmain.cpp.obj:winmain.cpp:(.text+0xcc8): undefined reference to `_imp__ilOriginFunc@4'
  CMakeFiles/DevILTest.dir/winmain.cpp.obj:winmain.cpp:(.text+0xce0): undefined reference to `_imp__ilEnable@4'
  CMakeFiles/DevILTest.dir/winmain.cpp.obj:winmain.cpp:(.text+0xcf9): undefined reference to `_imp__ilSetInteger@8'
  </code></pre>
  
  <p>If i remove the dll files and run the cmake skript the DevIL.lib library is localized correctly and i go no linker failures:</p>
  
  <pre><code>-- Detected OpenGL path is : glu32;opengl32
  -- Found DevIL includes at: C:/mingw/include/IL
  -- Found DevIL library at: C:/mingw/lib/DevIL.lib
  </code></pre>
  
  <p>But when in this case the applicaton crashes on start up while missing the dll files. If i add them now back to mingw or application root the application runs, but fails again on cmake execution while localize the dll files instead of .lib ...</p>
  
  <p>Has anyone an idea how i could solve this issue? 
  I would be deeply gratefull for any hint.
  Best regards, 
  Christian</p>