[libc] [llvm] [libc] delete hdrgen (PR #117220)

[Paul Kirth via llvm-commits]

ilovepi wrote:

Hi, I think something in the Windows configs may have been missed. we're seeing the following CMake error on our Windows bot:
```
CMake Error at C:/b/s/w/ir/x/w/llvm-llvm-project/libc/CMakeLists.txt:359 (message):
  C:/b/s/w/ir/x/w/llvm-llvm-project/libc/config/windows/headers.txt file not
  found and fullbuild requested.


-- Configuring incomplete, errors occurred!
```

Bot link:  https://ci.chromium.org/ui/p/fuchsia/builders/toolchain.ci/clang-windows-x64/b8729538683736875265/overview

Logs: https://logs.chromium.org/logs/fuchsia/buildbucket/cr-buildbucket/8729538683736875265/+/u/clang/configure/stdout

I assume there's just some missing CMake line for windows that was missed, but I'm not super familiar w/ the libc build. Do you have an idea of where that would be?

https://github.com/llvm/llvm-project/pull/117220