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

[Arthur Eubanks via cfe-commits]

aeubanks wrote:

yeah that patch makes those test pass with this PR, lgtm

(you could also test locally by touching the files I mentioned above, e.g. even just `touch lib/clang/19/lib/linux/libclang_rt.builtins-aarch64-android.a` repro'd the test failure on my machine)

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