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

[Joseph Huber via llvm-commits]

jhuber6 wrote:

> > The GPU loader utilities still need this weird "forced projects" thing.
> 
> Wait, that should be orthogonal to old vs new hdrgen. If anything, we probably need to rethink #117265.

It's fine, it doesn't build anything `libc` related, just a handful of utilities. The only `libc` thing they depend on is the `printf` converter stuff, if we moved that to a shared location we could just make it an LLVM utility or something.

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