[libc-commits] [libc] [libc] document supported os ranges (PR #118863)

[Nick Desaulniers via libc-commits]

nickdesaulniers wrote:

> but doesn't have the kernel version info.

https://syscalls.mebeim.net/?table=x86/64/x64/latest looks handy.

https://github.com/llvm/llvm-project/pull/118863