"/usr/bin/g++" is used by qmake, but "/usr/bin/gcc" is configured in the kit.
please update your kit of choose a mkspec for qmake that matches your target environment better.
couldn't find any way how to change the complier used by qmake to match the one configured by the kit.
one Tools > Options > Build & Run > kit . there is no way to change the qmake complier back to gcc. and the problem is there is only gcc and clang auto detected by qt 5.9
The problem was that i installed Two versions of Qt and i think there config or something overlapped so the g++ option didn't appear until i remove both versions and installed Qt 5.9.1 again the g++ option appeared and now i don't have the issue any more .