This line was OK for harcoded builtins (if there's a syntax error in the baked-in stdlib then jq is pretty broken), but we need to handle errors in a user-written library more elegantly. If nerrors > 0 then it's already printed them to stderr, but you should `block_free(b)` and propagate the error back to `main`.

`builtins_bind` and `builtins_bind_one` may need to take a `block*` which they modify and return an error code or something similar.