2635212b77
Since Yarn 3.1.0, some cache items no longer have checksums, mostly derived items like patched packages. Nixify skipped these, but that has started causing `--immutable-cache` to complain about the missing entries. Instead, we will have to rely on the Nix sandbox for purity, so that Yarn only does local operations (like patching) when to fill in these missing cache entries.