SuperBuild: make sure shark library goes to install/lib

SuperBuild/CMake/External_shark.cmake

@@ -45,6 +45,7 @@ ExternalProject_Add(SHARK
   -DENABLE_HDF5:BOOL=OFF
   -DENABLE_CBLAS:BOOL=OFF
   -DENABLE_OPENMP:BOOL=${OTB_USE_OPENMP}
+  -DSHARK_INSTALL_LIB_DIR:STRING=lib/
   ${SHARK_SB_CONFIG}
   CMAKE_COMMAND ${SB_CMAKE_COMMAND}
   LOG_DOWNLOAD 1