clang++ -ccc-gcc-name g++ -Wl,-rpath,/home/yigo/Qt5.12.12/5.12.12/gcc_64/lib -o Test1 main.o mainwindow.o moc_mainwindow.o   /home/yigo/Qt5.12.12/5.12.12/gcc_64/lib/libQt5Widgets.so /home/yigo/Qt5.12.12/5.12.12/gcc_64/lib/libQt5Gui.so /home/yigo/Qt5.12.12/5.12.12/gcc_64/lib/libQt5Core.so -lGL -lpthread   

/usr/bin/ld: cannot find -lGL: No such file or directory

solution:

sudo apt install mesa-common-dev libglu1-mesa-dev

Qt error: /usr/bin/ld: cannot find -lGL: No such file or directory_qt

It works.

​c++ - /usr/bin/ld: cannot find -lGL (Ubuntu 14.04) - Stack Overflow​