[lld] [lld] check cache in loadDylib before real_path (PR #143595)

[Richard Howell via llvm-commits]

rmaz wrote:

> Can we add a test case that would have crashed the previous PR?

Tricky to manage in a unit test, but i'll try and come up with a test that fails without this change involving re-exported library names and symlinks.

https://github.com/llvm/llvm-project/pull/143595