[HIP] Allow the new driver to compile HIP in non-RDC mode

The new driver primarily allows us to support RDC-mode compilations with
proper linking. This is not needed for non-RDC mode compilation, but we
still would like the new driver to be able to handle this mode so we can
transition away from the old driver in the future. This patch adds the
necessary code to support creating a fatbinary for HIP code generation.

Reviewed By: yaxunl

Differential Revision: https://reviews.llvm.org/D129784