[llvm] [runtimes] Add a missing LLVM_LIBDIR_SUFFIX (PR #159758)

[Tulio Magno Quites Machado Filho via llvm-commits]

tuliom wrote:

It looks like the armv8 tests on buildkite got cancelled.
That shouldn't be related to this PR.

https://github.com/llvm/llvm-project/pull/159758