Fix doxygen folder

CMakeLists.txt

@@ -671,7 +671,7 @@ if(DOXYGEN_FOUND)
     COMMAND ${DOXYGEN_EXECUTABLE} -u ${DOXYGEN_DOXYFILE}
     COMMAND ${DOXYGEN_EXECUTABLE} ${DOXYGEN_DOXYFILE}
     COMMAND ${CMAKE_COMMAND} -E echo "Done."
-    WORKING_DIRECTORY ${PROJECT_SOURCE_DIR}/doxygen
+    WORKING_DIRECTORY ${PROJECT_SOURCE_DIR}/docs/doxygen
   )
 
   # Add the "view_docs" target that opens the generated API documentation.