As far as I know, Qt is not installed by default in /usr/lib/x86_64-linux-gnu/qt4. That directory is the default path when linux detects a dependency which requires Qt.
Where did you installed Qt? How did you installed it? Did you set the PATH environment variable to where Qt binaries are installed?
Usually, you have to follow the next steps:
- 1.- Install the the basic requirements for building Qt applications.
- 2.- Download Qt. I recommend Qt 5 using an offline installer. Otherwise, you'd need to compile from the source. Here you have a list of older versions of Qt.
- 3.- Set the environment variable
PATH to the directory where you Qt bin directory is installed.
qmake && make && make install- Sebastian Lange