When using CMake >= 3.24 use CMAKE_COMPILE_WARNING_AS_ERROR variable instead of setting -Werror directly

[traversaro]

The -Werror option is typically enabled automatically by library authors, so they ensure that all contributors to the library early fail if new code they write contain a warning, ensuring as soon as possible that no new warnings are added to the library. On the other hand, people that package libraries for distributions prefer to disable the -Werror option, as they may want to compile a given library with a new compilers (that may not have even existed when a given release of a library was tagged), that introduce new warnings, without having a failure. For a detailed discussion of this from the point of view of people packaging libraries, see https://youtu.be/_5weX5mx8hc?si=ZtiWaK7KPTfQ01_g&t=322 .

Thanks to the CMAKE_COMPILE_WARNING_AS_ERROR CMake option available since CMake 3.24, it is possible to have the best of both worlds. Library authors can define this variable as an option and have it ON by default, while people packaging libraries can just set it to OFF from CMake command line invocation (or pass --compile-no-warning-as-error option to CMake) to have build scripts that will work also with more recent compilers.

[christian-rauch]

This generally makes sense with the "support newer compilers" argument. But we can reuse the --compile-no-warning-as-error flag instead of adding a new option.

[christian-rauch]

Can you rebase and squash your commits together?

[traversaro]

Can you rebase and squash your commits together?

Done.

[christian-rauch]

Thanks.