[libc] [llvm] [libc][c11] Add stdio.h's rename() function (PR #85068)

[Nick Desaulniers via llvm-commits]

https://github.com/nickdesaulniers approved this pull request.

looks great! Thanks for the PR. Do you have permissions to merge, or do you need one of us to do that for you?

https://github.com/llvm/llvm-project/pull/85068