[llvm] [test] Align behavior of interrupts.test on different platforms (PR #68556)

[James Henderson via llvm-commits]

jh7370 wrote:

> Thank you for clarification. In the new fix stderr is propagated to calling process so we can get actual stderr of `llvm-symbolizer`. When llvm-symbolizer starts complaining on missed 'foo', we could replace
> 
> ```
> # RUN: count 0 < %t.err`
> ```
> 
> with
> 
> ```
> # RUN: FileCheck --input-file=%t.err %s
> # CHECK: {{.*}} error: 'foo': {{[Nn]}}o such file or directory
> # CHECK-NOT: {{.+}}
> ```
> It should be enough to make the check you intended, no?
> ```

This sounds reasonable to me.

https://github.com/llvm/llvm-project/pull/68556