rts/linker/LoadArchive: Don't rely on file extensions for identification of archive members

Ben Gamarirequested to merge
wip/T130103 into master

Previously we would rely on members' file extensions to determine which are loadable objects. This is naturally fragile and broken when the user would change the object suffix (e.g. #24230 (closed)).

Fixes #13103 (closed).

Merge request reports