[clang] [HIP][Clang][Driver] Move BC preference logic into ROCm detection (PR #149294)

[Jakub Chlanda via cfe-commits]

jchlanda wrote:

No new tests are added in this patch, but the expected behaviour should not change and existing tests cover it:
* [amdgpu-openmp-toolchain.c](https://github.com/jchlanda/llvm-project/blob/jakub/rocm_detection/clang/test/Driver/amdgpu-toolchain.c#L1)
* [hip-device-libs.hip](https://github.com/jchlanda/llvm-project/blob/jakub/rocm_detection/clang/test/Driver/hip-device-libs.hip#L1)
* [rocm-device-libs.cl](https://github.com/jchlanda/llvm-project/blob/jakub/rocm_detection/clang/test/Driver/rocm-device-libs.cl#L1)

https://github.com/llvm/llvm-project/pull/149294