[clang] [Clang] Search for 'offload-arch' only next to the clang driver (PR #150965)

[Joseph Huber via cfe-commits]

jhuber6 wrote:

> Is clang tools always installed?

Yes, but if they somehow weren't this would just become an error for native detection, nothing catastrophic.

https://github.com/llvm/llvm-project/pull/150965