Wouldn’t this be on the project level rather than to be built into the standards? For cmake projects we should strive for config ones, but some projects are dead set on not supporting cmake. I don’t see a good way to incorporate with those other than FindPackage.cmake. For non-cmake projects I think it makes sense to combine them there.
Also because FindPackage.cmake is generally unregulated, I think it is on equal footing with FetchContent and ExternalProject wince for those you also should define the compilation options.