[llvm] [libc] Deprecate LLVM_ENABLE_PROJECTS in favor of LLVM_ENABLE_RUNTIMES. (PR #117265)

[Nick Desaulniers via llvm-commits]

nickdesaulniers wrote:

It sounds like we might need to rethink this for the gpu build's host utilities.

https://github.com/llvm/llvm-project/pull/117220#pullrequestreview-2476305981

https://github.com/llvm/llvm-project/pull/117265