Unify WarningFlags.cmake by checking if compiler supports warning flag

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Instead of having different warning flags per compiler, check for each flag if the compiler supports it and then add it

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#3029 for reference

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https://www.foonathan.net/2018/10/cmake-warnings/

The trick is to use target_include_directories(my_library SYSTEM PUBLIC include/). The SYSTEM turns the include directory into a system include directory. Compilers will not issue warnings from header files originating from there.