[ELF] Reimplement unknown -z options using the isClaimed bit

Maintaining the long list of known -z options
(https://reviews.llvm.org/D48621) turns out to be cumbersome. Go the
D48433 route instead.

max-page-size/common-page-size are claimed when `target` is available.

Inspired by: https://reviews.llvm.org/D48433