tinyxml2 find

Former-commit-id: de85afc5ac20ec622a41f1f975ea921563e4394c

tutorial/cmake/FindTINYXML2.cmake

@@ -10,6 +10,7 @@ FIND_PATH(TINYXML2_INCLUDE_DIR tinyxml2.h
    /usr/local/include
    ${PROJECT_SOURCE_DIR}/../libigl/external/tinyxml2/
    ${PROJECT_SOURCE_DIR}/../../external/tinyxml2/
+   ${PROJECT_SOURCE_DIR}/../external/tinyxml2/
    ${PROJECT_SOURCE_DIR}/external/tinyxml2/
 )