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

[Nico Weber via cfe-commits]

nico wrote:

This is a behavior change: In distributed build environments, neither lib file exists at compile time. Previously, this would result in the "old" style, now (together with #81037) it results in the "new" style (which we disable everywhere since it causes all kinds of issues – from what I can tell, we're not alone in this).

Is there some way we can tell clang that we always want the old style here, independent of what's on disk?

[ttps://crbug.com/335997052](https://crbug.com/335997052) has details.

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