[llvm] [CMake] Special-case HarmonyOS hosts in get_host_triple() (PR #219882)

[via llvm-commits]

finagolfin wrote:

How are you testing this, in an emulator or actual hardware? I see that [their new programming language, Cangjie, uses LLVM](https://jcst.ict.ac.cn/article/cstr/32374.14.s11390-025-5978-7), have you checked to see how they handle this config in their OSS compiler source?

https://github.com/llvm/llvm-project/pull/219882