[llvm] [CMake] Correctly handle LLVM_ENABLE_RUNTIMES in targets (PR #69869)

[Jonas Devlieghere via llvm-commits]

JDevlieghere wrote:

@ldionne pointed me at the `runtimes` target (which seems like the right thing to do regardless of this change) so I've changed the lldb build to depend on that (dfa3570). 

https://github.com/llvm/llvm-project/pull/69869