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A general description is here.
It reports the OS in use (if known, as given by ‘osVersion’) as well as that R was built for.
It notes if a C++ standard was specified which is older than the current default: many packages have used C++11 to mean ‘not C++98’ - as C++11 is the minimum supported since R 4.0.0, that specification can probably be removed.
Where a C++ standard is specified, it is reported.