[llvm] [Target] Change `no-trap-after-noreturn` to `trap-after-noreturn` (PR #67925)

[Fangrui Song via llvm-commits]

MaskRay wrote:

> OK. If the naming was intentional, I'm fine keeping it as is.

I think a variable with a positive meaning (`TrapAfterNoreturn`) is preferred.  You could make the change non-functional.

It's just that how `TrapAfterNoreturn` is set to true and false should be thought carefully.

https://github.com/llvm/llvm-project/pull/67925