[llvm] [llvm][object] Expose `writeArchiveToStream` (PR #98254)

[Jeff Niu via llvm-commits]

Mogball wrote:

Hey thanks for taking a look! I found it odd that the only exposed APIs for writing a new archive were directly to a file or to a memory buffer. I have a use case where it would be more efficient to write directly to a stream to avoid copying out of the memory buffer. If you're not happy with this change, I'm more than willing to revert it for now

https://github.com/llvm/llvm-project/pull/98254