[libunwind] [libunwind] Remove unnecessary dependencies on fprintf and stdio.h for increased baremetal friendliness (PR #72040)

[Louis Dionne via cfe-commits]

ldionne wrote:

The CI issues are flakes (we just made major changes to our infrastructure and we're still adjusting). I think this is good to go.

https://github.com/llvm/llvm-project/pull/72040