Not strange. You're not passing this location to the compiler.
./configure --with-frontend='xforms qt' --with-qt-includes=/usr/include/qt3
Ok now it works.
Why this qt includes dir is not configure automatically from the ./configure script. ?
Not strange. You're not passing this location to the compiler.
./configure --with-frontend='xforms qt' --with-qt-includes=/usr/include/qt3