broken build: std::result_of is removed in C++20

[niclar]

-Can you make the usage of the now deprecated and removed std::result_of conditional on the C++ revision. C++2x builds are now broken.

HEAD: adbed1b

[elBoberido]

@niclar I think this is easy to fix. It should be possible to add a language version switch in iceoryx_platform/linux/include/iceoryx_platform/platform_settings.hpp similar to what is done in iceoryx_platform/linux/include/iceoryx_platform/attributes.hpp. I might also be a good idea to move the invoke_result alias somewhere else since it is a bit out of place in platform_setting.hpp

@elfenpiff @mossmaurice Objections? Ideas?

[niclar]

as a temporary workaround one can override the removal as;

if(WIN32)
    add_compile_definitions(_HAS_DEPRECATED_RESULT_OF)
else()
    add_compile_definitions(_LIBCPP_ENABLE_CXX20_REMOVED_TYPE_TRAITS)
endif()

[elBoberido]

@niclar sure, but we already have the machinery to use invoke_result for C++17 and above. No need to rely on deprecated functionality on newer C++ standards. We just have to do the same we did with attributes.hpp and add a language version switch. On macOS and Windows we already use std::invoke_result.

Would you like to implement this?