Linux 4.15? Are you running a disro or a Linux from scratch type of thing?
I think if the gui isn't installed, you should check how you ran [dot]/configure (my autocorrect won't let me print a dot). If you didn't add any extra commands then it'll be the dependencies you installed. There are additional ones for gui usage, I'll write them below when I edit this post:
Edited:
sudo apt-get install libqt5gui5 libqt5core5a libqt5dbus5 qttools5-dev qttools5-dev-tools
Even if you did it last time it doesn't hurt to do it again and if the build still fails, take each install command individually and try to see where the error lies...