--check: Fix "failed to produce output path"
--check: Fix "failed to produce output path"

This occured when sandbox building is disabled, at least one output
exists, and at least one other output does not.

bennofs/nix,dtzWill/nix,ehmry/nix,dezgeg/nix,ysangkok/nix,ehmry/nix,layus/nix,ysangkok/nix,shlevy/nix,dezgeg/nix,NixOS/nix,vcunat/nix,ehmry/nix,wmertens/nix,ysangkok/nix,ehmry/nix,vcunat/nix,peti/nix,rycee/nix,pikajude/nix,bennofs/nix,wmertens/nix,zimbatm/nix,rycee/nix,shlevy/nix,dtzWill/nix,dtzWill/nix,dtzWill/nix,ehmry/nix,zimbatm/nix,shlevy/nix,peti/nix,bennofs/nix,dtzWill/nix,rycee/nix,ehmry/nix,peti/nix,rycee/nix,dezgeg/nix,pikajude/nix,zimbatm/nix,layus/nix,layus/nix,NixOS/nix,layus/nix,pikajude/nix,rycee/nix,shlevy/nix,dezgeg/nix,NixOS/nix,bennofs/nix,wmertens/nix,peti/nix,shlevy/nix,layus/nix,NixOS/nix,vcunat/nix,NixOS/nix,zimbatm/nix,vcunat/nix,peti/nix,dezgeg/nix,wmertens/nix