Adapt to latest Zig master

See ziglang/zig/pull/10055

generator/main.zig

@@ -8,7 +8,7 @@ pub fn main() !void {
 
     var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
     defer arena.deinit();
-    const allocator = &arena.allocator;
+    const allocator = arena.allocator();
 
     var args = std.process.args();
     const prog_name = try args.next(allocator) orelse return error.ExecutableNameMissing;