I got the following build error
"src/checks/level2/missing-qobject-macro.cpp:93:43: error: 'std::filesystem' has not been declared".
I'm pretty sure that my compiler (gcc 11.2.0) supports it and cmake seems to agree and defines -DHAS_STD_FILESYSTEM. It turns out that the manual addition of "-std=c++14" to CMAKE_CXX_FLAGS overwrote "CMAKE_CXX_STANDARD 17" here. Seems generally nicer to only have that in one place and it also fixes the previously mentioned build error.