compiletest: check_no_compiler_crash doesn't catch non-ICE panics

[cuviper]

As noted in #49826 (comment), currently rustc is panicking on compile-fail/issue-36638 (which I will file as a separate bug), but compiletest does not detect this because it's also not caught as an ICE (to be fixed by #49826). In check_no_compiler_crash, it only looks for the literal string "error: internal compiler error".