[OpenMP] Initial Implementation of LTO and bitcode linking in linker wrapper

This patch implements the fist support for handling LTO in the
offloading pipeline. The flag `-foffload-lto` is used to control if
bitcode is embedded into the device. If bitcode is found in the device,
the extracted files will be sent to the LTO pipeline to be linked and
sent to the backend. This implementation does not separately link the
device bitcode libraries yet.

Depends on D116675

Differential Revision: https://reviews.llvm.org/D116975