[libc-commits] [libc] [libc] Add base for target config within cmake (PR #72318)

[via libc-commits]

https://github.com/lntue commented:

So currently we (potentially) include multiple `config.json` files.  I think each build should only has 1 single `config.json`, similar to `entrypoints.txt`, and should be put in the same path.  If multiple architectures on the same OS want to share some configs, then they should explicitly include the shared `config.json` inside their own `config.json`.

Another the thing we should do is probably refactor all of these logic into `LibcConfig` file.

All of these improvements can be done in the followup changes.  This PR is good to me as it is to enable the feature.

https://github.com/llvm/llvm-project/pull/72318