Annotate options with completion information

This is a quite boring patch, just adding annotation information to
all existing options. Some of the annotations are not very good; but
we don't have support for more precise completion in
build-bash-completion, so this is good enough.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Agata Murawska <agatamurawska@google.com>