Close almost all file descriptors in the builder
Close almost all file descriptors in the builder

This regression was accidentally introduced in
35355fc1fcffbe859395e360c0a6a1463f137d63.

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