[HIP] Ignore host linker flags for device-only

When compiling in device only mode (e.g. --offload-device-only), the
host linker phase would not happen and therefore, the driver should
ignore all the host linker flags.

Differential Revision: https://reviews.llvm.org/D154881

Change-Id: I8244acef5c33108cf15b1dbb188f974f30099718