[libc] [llvm] [libc] Allow each function can have extra attributes by defining LLVM_LIBC_FUNCTION_ATTR_func macro. (PR #116160)

[Alexey Samsonov via llvm-commits]

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

LGTM, but please get confirmation from @nickdesaulniers  as well.

https://github.com/llvm/llvm-project/pull/116160