[CMake] check_cxx_source_compiles and include directories

[Roman Wüger]

Hello,

I've a small code example to test if the <mutex> header file exists (with check_cxx_source_compiles), which sets my variable successfully to TRUE.

When I compile the real code then I got an error message saying 'mutex' file not found.

I checked the compile flags for both situations and these are equal. So I thought that the include directories could be the problem.

Any hints?

Best Regards
Roman