[llvm] [llvm] Allow Rust personality name to contain arbitrary prefix (PR #166095)

[via llvm-commits]

Noratrieb wrote:

`test\Analysis\CostModel\AArch64\sincos.ll:41:17: error: SINCOS_STRET: expected string not found in input` failed on both Linux and Windows, which seems like an unrelated failure? https://github.com/llvm/llvm-project/actions/runs/19079423980/job/54529717418

I rebased against latest main and ran `check-llvm` locally on my Linux system and all tests passed (I didn't do that originally because I had some trouble getting LLVM to build, but now it worked)

https://github.com/llvm/llvm-project/pull/166095