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

[Fangrui Song via llvm-commits]

MaskRay wrote:

We can disable the test on -DLLVM_ENABLE_PER_TARGET_RUNTIME_DIR=OFF layouts, but I don't find a lit feature that.

The usual way is to create a compiler-rt file hierarchy under `Inputs`. Just `fd libclang_rt.builtins.a` for some examples.

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