This is a follow on to D119107. AIX ld now supports libLTO loaded
as a plugin
This change teaches the clang driver how to pass AIX ld the
libLTO path and the option to pass LTO significant driver options
through to the plugin. Some remarks plugin options are mapped
to their libLTO equivalents when using the AIX ld.
We need also to indicate to the toolchain that we now support
bitcode in the linker, or we run into asserts on some single-step
LTO invocations.
See also https://www.ibm.com/docs/en/aix/7.2?topic=l-ld-command for
the linker interface.
co-authored-by: Ettore Tiotto <etiotto@ca.ibm.com>
co-authored-by: Wai Hung Tsang <whitneyt@ca.ibm.com>
clang-format: please reformat the code