Forcibly rebuild package while ignoring cached fixed-output derivations (`fetchurl` & co)

My system config is failing to build in CI because a variety of elpa projects have decided to update tarballs without a version change (seems to be related to emacs 28 being released?).

Because these inputs are all downloaded using fetchurl, they’re all FODs, and therefore I can’t locally reproduce this, but I need to fix it before my system update can succeed properly.

As annoying as this upstream behavior is, it’s to be expected that some upstreams will do that, and I don’t have the resources to mirror every input all my computers use, so occasionally I’ll have to work through this.

Can I somehow quickly rebuild that package without its cached FODs locally so I can tell how widespread this is? I’m one package into this, and it’d be incredibly tedious to wait 20 minutes for my CI to get to that point every time I fix a checksum downstream.