[clang] [llvm] [offload-arch] Move GPU detection into a library and unit tests to unittests/tools (PR #226552)

[Nikita Kornev via llvm-commits]

KornevNikita wrote:

> FYI, no need to update gn (or bazel) build files. LLVM's official build system is CMake. The other build systems are updated by folks who maintain them.

should I undo this?

https://github.com/llvm/llvm-project/pull/226552