For small QT development on N900 itself - Standard Maemo 5 repository (both - maemo.org and Nokia) doesn't have ARMEL binaries in libqt4-dev (see bug https://bugs.maemo.org/show_bug.cgi?id=11445) since PR1.2. So, to run qt4 qmake/uic/moc compilers/builders - get and install libqt4-dev-armel package from https://garage.maemo.org/projects/libqt4-dev-arm/ instead of libqt4-dev