[libc-commits] [libc] [libc][docgen] regen docgen via cmake (PR #119628)

[Nick Desaulniers via libc-commits]

nickdesaulniers wrote:

So it looks like clang itself copies its rst files into the build dir.  I can emulate the approach I think.

`copy-clang-rst-docs`

https://github.com/llvm/llvm-project/pull/119628