[Clang] Remove direct linking of offloading runtimes from the arch tools

The tools `amdgpu-arch` and `nvptx-arch` are used to query the supported
GPUs on a system to implement features like `--offload-arch=native` as
well as generally being useful for setting up tests. However, we
currently directly link these if they are availible. This patch removes
this because it causes many problems on the user not having the libaries
present or misconfigured at build time. Since these are built
unconditionally we shoudl keep the dependencies away from clang.

Fixes https://github.com/llvm/llvm-project/issues/62784

Reviewed By: ye-luo

Differential Revision: https://reviews.llvm.org/D150807