@(linkage=<string>) for procedures and variables; @(require) for procedures; package runtime linkage improvements; Subsequence improvements to lb_run_remove_unused_function_pass

src/checker.hpp

@@ -102,6 +102,7 @@ struct AttributeContext {
 	String  link_name;
 	String  link_prefix;
 	String  link_section;
+	String  linkage;
 	isize   init_expr_list_count;
 	String  thread_local_model;
 	String  deprecated_message;