I am using Pop!OS, a derivative of Ubuntu 18.04 LTS.
libqt5serialport5 was already installed & updated, so I installed libqt5serialport5-dev.
$ sudo apt install libqt5serialport5 libqt5serialport5-dev
...
libqt5serialport5 is already the newest version (5.9.5-0ubuntu1).
libqt5serialport5-dev is already the newest version (5.9.5-0ubuntu1).
I get the same message.
~/Downloads/klog-0.9.8$ qtchooser -l
4
5
default
qt4-x86_64-linux-gnu
qt4
qt5-x86_64-linux-gnu
qt5
~/Downloads/klog-0.9.8$ export QT_SELECT=qt5
~/Downloads/klog-0.9.8$ echo $QT_SELECT
qt5
~/Downloads/klog-0.9.8$ qmake PREFIX=/usr/local KLog.pro
Project MESSAGE: Building KLog 0.9.8
Project MESSAGE: Qt 5.9.5 in /usr
Project MESSAGE: Sources
Project MESSAGE: Other files
Project MESSAGE: More...
Project MESSAGE: Translations
Project MESSAGE: End of translations...
/home/duke/Downloads/klog-0.9.8/KLog.pro:240: message(message) requires one argument.
Project MESSAGE: Else...