Regression test `println!()` panic message on `ErrorKind::BrokenPipe`
No existing test (that I could find) failed if the `panic!()` of the `println!()` family of functions was removed, or if its message was changed:
104f4300cf/library/std/src/io/stdio.rs (L1007-L1009)
So add such a test.
This is in preparation of adding a hint about the existence of [`unix_sigpipe`](https://github.com/rust-lang/rust/issues/97889) if that is the reason for the panic.
Even if we don't end up adding a hint, this is still a sensible test to have, I think.
`@rustbot` label +A-testsuite +A-io +T-libs +O-unix
6cacb5247f