QMAKESPEC has not been set, so configuration cannot be deduced

[javi]

I know is an old issue, but still unanswered...

Maybe the error is because you didn't load the QMAKESPEC env variable. You can look the ones you can choose on /usr/share/qt4/qmakespec (or qt3, depending)

set env QMAKESPEC linux-g++ (or instead linux-g++, yours)

In the compilation directory:

qmake -project
qmake
make