CMakeLists.txt: Added Wundef warning to clang and gcc. (#1823)
CMakeLists.txt: Added Wundef warning to clang and gcc. (#1823)

Co-authored-by: Martin Wührer <0cc5484fad6410b8b922cfd45e7771171ab690eb@artech.at>
cppformat/cppformat,cppformat/cppformat,cppformat/cppformat,alabuzhev/fmt,alabuzhev/fmt,alabuzhev/fmt