[Interest] Static Qt 5.6.0 on Linux cannot find any fonts

[Nikos Chantziaras]

A statically built Qt 5.6.0 results in this when trying to run any 
application built with it:

QFontDatabase: Cannot find font directory 
/home/realnc/opt/qt-5.6/lib/fonts - is Qt installed correctly?

The application is completely lacking any text.

 From what I was able to find, it seems I have to bundle fonts with the 
executable and set QT_QPA_FONTDIR to my bundled fonts directory? That 
just doesn't sound right. The end user should be able to use the system 
fonts.

How do I make that happen?