[compiler-rt] Work around a C language bug in libFuzzer (PR #96775)

[David Benjamin via llvm-commits]

davidben wrote:

An alternate fix would be to give up on the libc functions and instead use `std::copy_n` and `std::equal`. Those do not share the same flaw. I stuck with the libc functions because I didn't see evidence of libFuzzer using much of `<algorithm>`'s functions here, but happy to do that if preferred. (That's how I usually fix C++ code.)

https://github.com/llvm/llvm-project/pull/96775