[libc-commits] [libc] [libc] fwrite_unlocked: only return errno if an actual error occurred. (PR #167350)

[Michael Jones via libc-commits]

https://github.com/michaelrj-google approved this pull request.

LGTM, I forgot about system `errno` potentially being already set from an unrelated call

https://github.com/llvm/llvm-project/pull/167350