[lld] ReleaseNotes: add lld/ELF notes (PR #124508)

[Peter Smith via llvm-commits]

smithp35 wrote:

Suggestions for addition:
Assuming it has made the release, this is a potentially breaking change for some people.
*  https://github.com/llvm/llvm-project/pull/124068 Error for executable .note.GNU-stack unless -z execstack or -r
* [LLD] Deprecate --lto-basic-block-sections=labels (#110697) This option is now replaced by `--lto-basic-block-address-map`.

https://github.com/llvm/llvm-project/pull/124508