[clang] Reapply "[analyzer] Fix false positive in strchr/strrchr with constant args" (PR #212124)

[Balázs Benics via cfe-commits]

steakhal wrote:

Hmm, I wonder why other tests that pin the target triple didn't fail on your bot before. We never used this REQUIRES clause and we have plenty of tests using `x86_64-unknown-linux-gnu`

https://github.com/llvm/llvm-project/pull/212124