Compatibility Information in CPS Files

It would be nice if my CPS files could describe how my library was built without be prescriptive to downstream consumers about how they should build.

For instance, it would be helpful to know that my library was built for C++20. It would not be helpful for my library to require all of its users to use a specific flag setting the C++ standard to 20. That goes in a build toolchain file, a build configuration file, or something of that nature.

I expect this information would be used to quickly ascertain incompatibilities across dependencies in clear ways that are not possible at the moment. In fact, it's is possible at the moment that a mismatching C++ standard, for instance, will compile and link fine but cause runtime issues in an production environment.

No files, tests, or entry points are named. First clarify the CPS metadata and schema requirements for recording build compatibility without imposing downstream build settings; done means an agreed representation that can expose incompatibilities without prescribing consumer configuration.

Written by the indexing model from the issue text.