frontend: update bluelib api usage

frontend/cmd/assemble.c

@@ -2,7 +2,7 @@
 #include "cmd.h"
 
 #include <blue/cmd.h>
-#include <blue/object/string.h>
+#include <blue/ds/string.h>
 #include <blue/term.h>
 #include <errno.h>
 #include <ivy/asm/assembler.h>
@@ -127,7 +127,7 @@ static b_string *get_source_filename(const char *src_path)
 	}
 
 	if (b_string_get_size(name, B_STRLEN_NORMAL) == 0) {
-		b_string_release(name);
+		b_string_unref(name);
 		name = NULL;
 	}
 
@@ -184,8 +184,8 @@ static int assemble(const b_command *cmd, const b_arglist *args, const b_array *
 
 	int r = assemble_file(in_path, out_path);
 
-	b_string_release(in_name);
-	b_string_release(out_name);
+	b_string_unref(in_name);
+	b_string_unref(out_name);
 
 	return r;
 #if 0