Right now if we run `check-offload` for SPIR-V the DeviceRTL isn't used
because we pass `-nogpulib`.
Don't pass that, but also don't pass `--libomptarget-spirv-bc-path` yet
because the DeviceRTL is brand new so we don't want to error if it's not
present.
Signed-off-by: Nick Sarnie <nick.sarnie@intel.com>