[clang] [compiler-rt] ohos: fix ohos.c test case error with LLVM_ENABLE_PER_TARGET_RUNTIME_… (PR #121484)

[Peng Huang via llvm-commits]

phuang wrote:

Updated the cmake script to output error message if LLVM_ENABLE_PER_TARGET_RUNTIME_DIR is OFF for ohos targets.

https://github.com/llvm/llvm-project/pull/121484