qt - Qmake-qt5 set top project directory variable -

First of all, I have read that I have a project developed with qmake-qt4, and I want to port it to qmake-qt5 Will happen. First of all, I found that the TOP_PROJECT_DIR variable did not work in QMake-QT5 to set the variable in the top project directory to .qmake.cache.in. But when I moved this code into the .qumake.conf file in the top project directory in

  TOP_PROJECT_DIR = $$ PWD  

, then no effect is not. The variable TOP_PROJECT_DIR is empty in the root and other * .pro-files of the project. How can I set the value to a whole project in one place?