The logic was using incorrect flag versions. For example:
- -target= can't be a prefix, it must be --target=.
- --driver-mode can't appear on its own, value must be attached to it.
While fixing those, also changes the append logic to make use of new
--target=X format instead of the legacy -target X version.
In addition to that makes use of the OPTTable instead of hardcoded strings to
make sure helper also gets updated if clang's options are modified.