[llvm-objcopy] Drop GRP_COMDAT if the group signature is localized

See [GRP_COMDAT group with STB_LOCAL signature](https://groups.google.com/g/generic-abi/c/2X6mR-s2zoc)
objcopy PR: https://sourceware.org/bugzilla/show_bug.cgi?id=27931

GRP_COMDAT deduplication is purely based on the signature symbol name in
ld.lld/GNU ld/gold. The local/global status is not part of the equation.

If the signature symbol is localized by --localize-hidden or
--keep-global-symbol, the intention is likely to make the group fully
localized. Drop GRP_COMDAT to suppress deduplication.

Reviewed By: jhenderson

Differential Revision: https://reviews.llvm.org/D106782