[clang] [Driver] Ensure ToolChain::LibraryPaths is not empty for non-Darwin (PR #87866)

[Nico Weber via cfe-commits]

nico wrote:

>  I would suggest we revert this - and at least collect all the observed side effects and declare them before considering relanding it.

That sounds good to me. Do you have a list of PRs to revert?

> ... then we do still get the old name embedded.

Sure. The motivation on our side is a distributed compile service where the library doesn't exist on the remote end. This patch means we'll have to add knowledge about path layouts at link time to the remote setup at compile time. That's certainly doable, but kind of janky.

(What we'll actually do is use the flag from #89642 to disable all this guessing of libs and just explicitly pass the path to the lib at link time. So this won't actually affect us then, but reverting and relanding in one commit with a list of side effects still sounds like a good thing independent of that.)

https://github.com/llvm/llvm-project/pull/87866