[Libomptarget] Explicitly pass the OpenMP device libraries to tests (#68225)

Summary:
We have tests that depend on two static libraries
`libomptarget.devicertl.a` and `libcgpu.a`. These are currently
implicitly picked up and searched through the standard path. This patch
changes that to pass `-nogpulib` to disable implicit runtime path
searches. We then explicitly passed the built libraries to the
compilations so that we know exactly which libraries are being used.

Depends on: https://github.com/llvm/llvm-project/pull/68220

Fixes https://github.com/llvm/llvm-project/issues/68141