[clang] [compiler-rt] [llvm] Automatic removal of unused standard header (PR #192800)

[Alexis Engelke via cfe-commits]

https://github.com/aengelke requested changes to this pull request.

Why? Please add a motivation to the PR description. For larger changes/long-term efforts/adding CI checks, an RFC would be good.

>From a compile-time perspective, standard headers are not the problem, because many expensive ones get pulled in almost everywhere through Support/ headers anyway. If anything, we should focus on reducing unneeded includes from LLVM headers, also by using forward declarations where possible. Just focusing on standard headers provides little value, IMO.

https://github.com/llvm/llvm-project/pull/192800