quote the variable

Modules/FindOpenGL.cmake

@@ -139,7 +139,7 @@ IF (APPLE)
   SET (OPENGL_FOUND "YES")
   SET (OPENGL_GLU_FOUND "YES")
   SET (OPENGL_LIBRARIES "-framework AGL -framework OpenGL" CACHE STRING "OpenGL lib for OSX")
-  SET (OPENGL_LIBRARY ${OPENGL_LIBRARIES} CACHE STRING "OpenGL lib for OSX (for CMake 1.4)")
+  SET (OPENGL_LIBRARY "${OPENGL_LIBRARIES}" CACHE STRING "OpenGL lib for OSX (for CMake 1.4)")
   SET (OPENGL_gl_LIBRARY "-framework OpenGL" CACHE STRING "OpenGL lib for OSX")
   SET (OPENGL_glu_LIBRARY "-framework AGL" CACHE STRING "AGL lib for OSX")
 ENDIF (APPLE)