[lld] [lld-link] Do not assert when reporting error about non-thin archive (PR #159828)

[Nico Weber via llvm-commits]

nico wrote:

> Is it possible to make a test for this change?

Not easily, I think. You need a corrupt archive as input, which we don't have an easy way of creating as far as I know.

https://github.com/llvm/llvm-project/pull/159828