Unsolved Link manually built qt library to its qt source

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Hello. under linux, I built qt with debug symbols using ./configure -debug and a bunch of options. It finally was installed to /opt/alg/qt-5.8.0-centos and the sources are at /opt/alg/qt-5.8.0-src. I created a link src in the built and installed qt folder to the source folder. When using gdb in the terminal, I can see that I linked to the correct libraries and that the loading symbols were loaded, but it could not find the source on its own.

Now using Qt creator, I wuold like to be able to see the qt source code ( and its variable values ) when debugging. When I go to Tools->Options...->Debugger and I click on "Add Qt sources", it links the target path /opt/alg/qt-5.8.0-src to source path /var/tmp/qt-src, which correpsond to nothing and doesn't work. Replacing it by /opt/alg/qt-5.8.0-centos doesn't work either. So what should I do ?

Thank you for any help.