[LLD] lld does not parse options for orphan-handling in a case insensitive manner.

[quic-rb10]

Currently LLD does not parse options for orphan handling in a case insensitive manner.

The command:
ld.lld 1.o -orphan-handling=Error -T script.t
returns an error: ld.lld: error: unknown --orphan-handling mode: Error

However, GCC supports case insensitive parsing for -orphan-handling options and the above command works normally.

We should support case insensitive parsing in lld; this would help improve compatibility with GNU ld.

[MaskRay]

Thanks for reporting this difference. It looks like --orphan-handling in binutils is special in that it is case insensitive. Other options taking a string argument are all(?) case sensitive, e.g. --unresolved-symbols=. I don't think =Error is used widely. Actually, warn/error/discard are almost exclusively used in the wild.

Therefore, I don't think we should change lld code.