objtool: Upgrade "Linked object detected" warning to error

Force the user to fix their cmdline if they forget the '--link' option.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Brendan Jackman <jackmanb@google.com>
Link: https://lore.kernel.org/r/8380bbf3a0fa86e03fd63f60568ae06a48146bc1.1741975349.git.jpoimboe@kernel.org

tools/objtool/builtin-check.c

@@ -198,8 +198,8 @@ int objtool_run(int argc, const char **argv)
 		return 1;
 
 	if (!opts.link && has_multiple_files(file->elf)) {
-		ERROR("Linked object detected, forcing --link");
-		opts.link = true;
+		ERROR("Linked object requires --link");
+		goto err;
 	}
 
 	ret = check(file);