[llvm] [CodeGen] Do not emit TRAP for `unreachable` after `@llvm.trap` (PR #94570)

[Matt Arsenault via llvm-commits]

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

LGTM but it sounds wrong that we can't assume the trap_func is noreturn 

https://github.com/llvm/llvm-project/pull/94570