[llvm] [llvm-config] Make llvm-config --system-libs obey LLVM_USE_STATIC_ZSTD. (PR #93754)

[Kyle Huey via llvm-commits]

khuey wrote:

Bump. @MaskRay if you don't have time to look at this yourself can you at least refer it to someone who does? I can't set reviewers on this PR.

https://github.com/llvm/llvm-project/pull/93754