Merge pull request #1915 from nuclearsandwich/use-install-prefix-as-root-dir

Use CMAKE_INSTALL_PREFIX as ASSIMP_ROOT_DIR.

assimp-config.cmake.in

@@ -10,10 +10,7 @@
 # ASSIMP_LIBRARY_DIRS - link directories
 # ASSIMP_LIBRARIES - libraries to link plugins with
 # ASSIMP_Boost_VERSION - the boost version assimp was compiled with
-get_filename_component(_PREFIX "${CMAKE_CURRENT_LIST_FILE}" PATH)
-get_filename_component(_PREFIX "${_PREFIX}" PATH)
-get_filename_component(_PREFIX "${_PREFIX}" PATH)
-get_filename_component(ASSIMP_ROOT_DIR "${_PREFIX}" PATH)
+get_filename_component(ASSIMP_ROOT_DIR "@CMAKE_INSTALL_PREFIX@" REALPATH)
 
 if( MSVC )
   # in order to prevent DLL hell, each of the DLLs have to be suffixed with the major version and msvc prefix