Rollup merge of #109394 - krasimirgg:llvm-17-vec-panic, r=nikic

adapt tests/codegen/vec-shrink-panik for LLVM 17

After llvm/llvm-project@0d4a709 LLVM now doesn't generate references to panic_cannot_unwind:
https://buildkite.com/llvm-project/rust-llvm-integrate-prototype/builds/17978#0186ff55-ca6f-4bc5-b1ec-2622c77d0ed5/744-746

Adapted as suggested by ````@nikic```` on Zulip:
https://rust-lang.zulipchat.com/#narrow/stream/187780-t-compiler.2Fwg-llvm/topic/a.20couple.20codegen.20test.20failures.20after.20llvm.200d4a709bb876824a/near/342664944
>Okay, so LLVM now realizes that double panic is not possible, so that's fine.

Author: matthiaskrgr