Implement LegacySSHStore::buildDerivation()
Implement LegacySSHStore::buildDerivation()

This makes LegacySSHStore usable by build-remote and
hydra-queue-runner.

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