This patch removes some ancient options as a clean-up before moving
code-gen to use LTOBackend in D94487.
I think it would preferable to remove those ancient options, because
- There are no corresponding options in LTOBackend based tools,
- There are no unit tests for them,
- They are not passed through by Clang,
- At least for GNVLoadPRE, users could just use GVN's enable-load-pre.
Alternatively we could add support for those options to lto::Config &
co, but I think it would be better to remove them, unless they are
actually used in practice.