[llvm] [profcheck] Add unknown branch weight for inlined memchr calls. (PR #160964)

[Mircea Trofin via llvm-commits]

https://github.com/mtrofin commented:

LGTM but let's wait for @alanzhao1 to land #158743.

I'd be fine with decoupling and coming afterwards to patch this file with the new API introduced there, too.

https://github.com/llvm/llvm-project/pull/160964