[Feature request] Provide a way to export CXX_STANDARD property
C++ standard version often controls library ABI or even API. When the library provides a possibility to be build using different standard versions, it is important to export the version for clients via pkg-config or exported targets.
Because of the CXX_STANDARD_REQUIRED
property (and variable) determining the actual standard being used is non-trivial. Please provide a way to read the actual standard version from a target and a way to export it (INTERFACE_${LANG}_STANDARD
? Or, maybe, a way to ask CMake to inject the standard selection compiler flag into the target compile features?).