[llvm] [symbolizer] Empty string is not an error (PR #92660)

[James Henderson via llvm-commits]

jh7370 wrote:

> If `--obj` is not specified, `llvm-symbolizer` will try reading binary name from input, together with an address. This is a normal use case and users may want check the tool liveness as well. IIRC this is the mode used in compiler-rt tests.

Sorry, you're right. I misunderstood some behaviour I was seeing when experimenting locally with it. In that case, I don't think the idea of using `ECHO` really works at all, because we'll always find it impossible to distinguish `ECHO` from a file called `ECHO`.

In that case, as I don't have any alternative suggestions, I'm okay with you relanding the original patch. @dwblaikie any objections?

https://github.com/llvm/llvm-project/pull/92660