PR26150, Assertion when asm() defines global symbols, -flto and --start-group

If an archive map contains symbols that aren't actually defined by the
indexed element for any reason, then loading that element will leave
the symbol undefined (or common).  This leads to the possibility of
the element being loaded again should the archive be searched again
due to the action of --start-group/--end-group.  The testcase
triggering this problem was an archive containing fat lto objects,
with the archive map incorrectly created by ar rather than gcc-ar.

	PR 26150
	* ldlang.c (ldlang_add_file): Assert that we aren't adding the
	current end of link.next list again too.
	* ldmain.c (add_archive_element): Don't load archive elements
	again that have already been loaded.