[clang] [clang][InstallAPI] Introduce basic driver to write out tbd files (PR #81571)

[Cyndy Ishida via cfe-commits]

cyndyishida wrote:

In case anyone is interested, 
Here are relevant links for upstreaming `tapi` in LLVM: 
* [Inital RFC](https://discourse.llvm.org/t/rfc-open-sourcing-and-contributing-tapi-back-to-the-llvm-community/46214/24)
* [Continued RFC](https://discourse.llvm.org/t/rfc-continuation-of-tapi-into-llvm/52825)
* [Dev Talk](https://www.youtube.com/watch?v=B9li6EkD5zA)
* [Full TAPI sources](https://github.com/apple-oss-distributions/tapi), includes docs

https://github.com/llvm/llvm-project/pull/81571