nix-build: Respect -Q during evaluation
nix-build: Respect -Q during evaluation

Fixes #474

zimbatm/nix,wmertens/nix,ttuegel/nix,ttuegel/nix,layus/nix,NixOS/nix,vcunat/nix,pikajude/nix,dezgeg/nix,gebner/nix,garbas/nix,dtzWill/nix,shlevy/nix,joelmo/nix,peti/nix,aucampia/nix,offlinehacker/nix,peti/nix,joelmo/nix,joelmo/nix,ttuegel/nix,rycee/nix,offlinehacker/nix,NixOS/nix,rycee/nix,layus/nix,rowhit/nix,shlevy/nix,tchajed/nix,vcunat/nix,peti/nix,NixOS/nix,layus/nix,vizanto/nix,ehmry/nix,ysangkok/nix,ehmry/nix,dezgeg/nix,shlevy/nix,joelmo/nix,ehmry/nix,puffnfresh/nix,gridaphobe/nix,wmertens/nix,ehmry/nix,garbas/nix,zimbatm/nix,vizanto/nix,garbas/nix,ehmry/nix,acowley/nix,pikajude/nix,dtzWill/nix,tchajed/nix,bjornfor/nix,NixOS/nix,rowhit/nix,dezgeg/nix,rycee/nix,pikajude/nix,gebner/nix,peti/nix,tchajed/nix,gebner/nix,bennofs/nix,gridaphobe/nix,bennofs/nix,vizanto/nix,vcunat/nix,ttuegel/nix,gebner/nix,offlinehacker/nix,dezgeg/nix,ysangkok/nix,rycee/nix,gridaphobe/nix,gridaphobe/nix,shlevy/nix,bjornfor/nix,layus/nix,NixOS/nix,vizanto/nix,layus/nix,ysangkok/nix,wmertens/nix,rowhit/nix,puffnfresh/nix,dtzWill/nix,acowley/nix,dezgeg/nix,bjornfor/nix,garbas/nix,acowley/nix,aucampia/nix,puffnfresh/nix,wmertens/nix,shlevy/nix,rowhit/nix,aucampia/nix,tchajed/nix,ehmry/nix,dtzWill/nix,aucampia/nix,bennofs/nix,puffnfresh/nix,rycee/nix,garbas/nix,acowley/nix,bjornfor/nix,dtzWill/nix,vcunat/nix,zimbatm/nix,bennofs/nix,peti/nix,zimbatm/nix,offlinehacker/nix