[compiler-rt] [llvm] [openmp] [Runtimes] Default build must use its own output dirs (PR #168266)

[Michał Górny via llvm-commits]

mgorny wrote:

Unfortunately, the latest version causes regressions in offload tests:

```
# | '/usr/lib/llvm/22/bin/llvm-offload-device-info': command not found
# | '/usr/lib/llvm/22/bin/offload-tblgen': command not found
```

i.e. it's using system LLVM binary directory for just-built tools.

https://github.com/llvm/llvm-project/pull/168266