Bread – How long do breadcrumbs last

Dry biscuits (American 'biscuits' - not cookies), or anything other flour based quick bread that dried out - if you're trying to replicate the bread crumbs. You may be able to get by with a modified muffin recipe as well. You'll want to avoid fats and oils to reduce the moistness.

Yeast bread develops a particular flavor and larger hole structure than quick bread though. The flavor of a quick bread breadcrumbs should be slightly different, but in many dishes the subtle difference won't be overwhelming unless the breading is a 'star' of the dish. The hole structure really doesn't matter luckily - as developing that is a large part of the time factor of real bread.

Drying it out will be the harder part. The denser structure holds moisture better, so slice it thin and give it low, dry, long heat.

_{Personally, anything that you're going to make for the purpose of breadcrumbs that isn't just a substitute (like cereal, crackers, etc in the other answer), sounds like it'd be easier just to make a loaf of fast rise bread to me.}

There are a number of rice-based bread crumb replacements, but my experience with them is that they are more like rice sand than bread crumbs. You can try making you own from other gluten free products like waffles or maybe puffed rice cereal.