Fix building against Nix 1.10
Fix building against Nix 1.10

Fixes #12.

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