Almost all i686-linux tests got blocked because of this problem:
https://hydra.nixos.org/eval/1638038#tabs-now-fail
It regressed in PR #105462 (commit ad26cb9ee8).
Now I tested that at least some test got fixed:
nix build -f nixos/release-combined.nix nixos.tests.knot.i686-linux
This change won't even cause any rebuild on 64-bit platforms,
and using nix booleans seems nicer anyway.