Keep build directory if not all expected outputs were produced
Keep build directory if not all expected outputs were produced

Fixes issue #123 in Nixpkgs.

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