If you want to build qt applications with koxtoolchain you'll need to link statically against libstdc++, because system is too old for modern toolchains.
Add the following to your
pro file (of course edit the path first):
Code:
LIBS += /home/pazos/x-tools/arm-kobo-linux-gnueabihf/arm-kobo-linux-gnueabihf/lib/libstdc++.a
QMAKE_LFLAGS += -static-libstdc++
You can build Qt 4.8.5 with koxtoolchain without problems, but you'll need to repurpose Sergey's drivers for touchscreen, framebuffer and keypad (or luck into his sources and add these drivers to Qt, but it's more work)