[Merge][CMake] Merged revisions : 1720

Revision  r1720
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Correct prefix path.

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[[Imported from SVN: r1849]]

cmake/pkg/dune-istl-config.cmake.in

 if(NOT @DUNE_MOD_NAME@_FOUND)
 #compute installation prefix relative to this file
 get_filename_component(_dir "${CMAKE_CURRENT_LIST_FILE}" PATH)
-get_filename_component(_prefix "${_dir}/../.." ABSOLUTE)
+get_filename_component(_prefix "${_dir}/../../.." ABSOLUTE)
 
 #import the target
 #include("${_prefix}/lib/cmake/@DUNE_MOD_NAME@-targets.cmake")