brew.rb: don't re-export for external commands
brew.rb: don't re-export for external commands

`bin/brew` already sets up a bunch of environment variables. There's no
need to re-export them for external commands. (`HOMEBREW_LIBRARY_PATH`
and `HOMEBREW_CACHE` continue to be determined later in the Ruby code.)

AlexejK/homebrew,gawbul/homebrew,elgertam/homebrew,filcab/homebrew,ebouaziz/linuxbrew,dongcarl/homebrew,scorphus/homebrew,MartinDelille/homebrew,hanxue/homebrew,pcottle/homebrew,dunn/homebrew,michaKFromParis/homebrew-sparks,sferik/homebrew,drewwells/homebrew,vigo/homebrew,eighthave/homebrew,3van/homebrew,iostat/homebrew2,ear/homebrew,haihappen/homebrew,LinusU/homebrew,ybott/homebrew,pcottle/homebrew,alebcay/homebrew,influxdata/homebrew,Asuranceturix/homebrew,galaxy001/homebrew,skatsuta/homebrew,yumitsu/homebrew,apjanke/homebrew,DoomHammer/linuxbrew,reelsense/linuxbrew,emcrisostomo/homebrew,dericed/homebrew,iostat/homebrew2,brunchboy/homebrew,Chilledheart/homebrew,ExtremeMan/homebrew,jamer/homebrew,emcrisostomo/homebrew,johanhammar/homebrew,hongkongkiwi/homebrew,galaxy001/homebrew,iostat/homebrew2,georgschoelly/homebrew,bukzor/linuxbrew,decors/homebrew,quantumsteve/homebrew,tschoonj/homebrew,influxdb/homebrew,Red54/homebrew,AlexejK/homebrew,benjaminfrank/homebrew,elgertam/homebrew,iostat/homebrew2,Angeldude/linuxbrew,decors/homebrew,bigbes/homebrew,quantumsteve/homebrew,galaxy001/homebrew,slyphon/homebrew,sometimesfood/homebrew,hakamadare/homebrew,sometimesfood/homebrew,afh/homebrew,skinny-framework/homebrew,yazuuchi/homebrew,Homebrew/homebrew,filcab/homebrew,influxdata/homebrew,AlexejK/homebrew,Linuxbrew/linuxbrew,alebcay/homebrew,ryanfb/homebrew,totalvoidness/homebrew,BrewTestBot/homebrew,Asuranceturix/homebrew,scpeters/homebrew,josa42/homebrew,hongkongkiwi/homebrew,muellermartin/homebrew,getgauge/homebrew,kenips/homebrew,dongcarl/homebrew,recruit-tech/homebrew,SuperNEMO-DBD/cadfaelbrew,hongkongkiwi/homebrew,kodabb/homebrew,reelsense/homebrew,thinker0/homebrew,cprecioso/homebrew,eighthave/homebrew,booi/homebrew,reelsense/homebrew,ilovezfs/homebrew,mobileoverlord/homebrew-1,skatsuta/homebrew,youtux/homebrew,theeternalsw0rd/homebrew,royhodgman/homebrew,tutumcloud/homebrew,optikfluffel/homebrew,yazuuchi/homebrew,cscetbon/homebrew,lrascao/homebrew,Linuxbrew/linuxbrew,marcwebbie/homebrew,youtux/homebrew,LinusU/homebrew,AlexejK/homebrew,Angeldude/linuxbrew,sjackman/linuxbrew,gawbul/homebrew,vigo/homebrew,OJFord/homebrew,ybott/homebrew,jamer/homebrew,yumitsu/homebrew,SteveClement/homebrew,yazuuchi/homebrew,dalanmiller/homebrew,drbenmorgan/linuxbrew,Chilledheart/homebrew,Asuranceturix/homebrew,ebouaziz/linuxbrew,dericed/homebrew,dickeyxxx/homebrew,vigo/homebrew,Asuranceturix/homebrew,apjanke/homebrew,thinker0/homebrew,SteveClement/homebrew,deorth/homebrew,youtux/homebrew,cosmo0920/homebrew,polishgeeks/homebrew,elyscape/homebrew,sakra/homebrew,sakra/homebrew,sakra/homebrew,dickeyxxx/homebrew,frodeaa/homebrew,MartinDelille/homebrew,Homebrew/homebrew,OJFord/homebrew,jamer/homebrew,pcottle/homebrew,kodabb/homebrew,base10/homebrew,scpeters/homebrew,joshfriend/homebrew,TaylorMonacelli/homebrew,ryanfb/homebrew,ybott/homebrew,cosmo0920/homebrew,ablyler/homebrew,ralic/homebrew,scorphus/homebrew,LinusU/homebrew,DoomHammer/linuxbrew,kevinastone/homebrew,lrascao/homebrew,hakamadare/homebrew,polishgeeks/homebrew,sferik/homebrew,deorth/homebrew,redpen-cc/homebrew,MartinDelille/homebrew,afh/homebrew,esamson/homebrew,cprecioso/homebrew,recruit-tech/homebrew,ryanfb/homebrew,keith/homebrew,decors/homebrew,keith/homebrew,tutumcloud/homebrew,eighthave/homebrew,3van/homebrew,michaKFromParis/homebrew-sparks,base10/homebrew,booi/homebrew,saketkc/linuxbrew,alebcay/homebrew,drewwells/homebrew,Linuxbrew/linuxbrew,SuperNEMO-DBD/cadfaelbrew,muellermartin/homebrew,emcrisostomo/homebrew,dplarson/homebrew,Homebrew/linuxbrew,apjanke/homebrew,theeternalsw0rd/homebrew,SuperNEMO-DBD/cadfaelbrew,bigbes/homebrew,keith/homebrew,hanxue/homebrew,liamstask/homebrew,cprecioso/homebrew,Angeldude/linuxbrew,sometimesfood/homebrew,joshfriend/homebrew,dericed/homebrew,johanhammar/homebrew,dplarson/homebrew,mobileoverlord/homebrew-1,brunchboy/homebrew,ebouaziz/linuxbrew,Angeldude/linuxbrew,ear/homebrew,optikfluffel/homebrew,filcab/homebrew,totalvoidness/homebrew,drbenmorgan/linuxbrew,getgauge/homebrew,ablyler/homebrew,Red54/homebrew,TaylorMonacelli/homebrew,tschoonj/homebrew,royhodgman/homebrew,liamstask/homebrew,pcottle/homebrew,dunn/homebrew,liamstask/homebrew,dongcarl/homebrew,slyphon/homebrew,dongcarl/homebrew,joshfriend/homebrew,kodabb/homebrew,reelsense/homebrew,sometimesfood/homebrew,reelsense/linuxbrew,kevinastone/homebrew,decors/homebrew,benjaminfrank/homebrew,esamson/homebrew,yumitsu/homebrew,yazuuchi/homebrew,redpen-cc/homebrew,OJFord/homebrew,ilovezfs/homebrew,mkrapp/homebrew,deorth/homebrew,bigbes/homebrew,redpen-cc/homebrew,optikfluffel/homebrew,muellermartin/homebrew,BrewTestBot/homebrew,liamstask/homebrew,nandub/homebrew,Homebrew/homebrew,lrascao/homebrew,sjackman/linuxbrew,ExtremeMan/homebrew,marcwebbie/homebrew,SteveClement/homebrew,drewwells/homebrew,TaylorMonacelli/homebrew,chadcatlett/homebrew,scorphus/homebrew,tschoonj/homebrew,tutumcloud/homebrew,retrography/homebrew,marcwebbie/homebrew,treyharris/homebrew,influxdb/homebrew,Chilledheart/homebrew,bukzor/linuxbrew,optikfluffel/homebrew,georgschoelly/homebrew,retrography/homebrew,SteveClement/homebrew,getgauge/homebrew,nandub/homebrew,Asuranceturix/homebrew,recruit-tech/homebrew,filcab/homebrew,base10/homebrew,recruit-tech/homebrew,quantumsteve/homebrew,nandub/homebrew,dickeyxxx/homebrew,haihappen/homebrew,skatsuta/homebrew,retrography/homebrew,ExtremeMan/homebrew,slyphon/homebrew,vigo/homebrew,chadcatlett/homebrew,Linuxbrew/linuxbrew,kenips/homebrew,osimola/homebrew,gicmo/homebrew,dutchcoders/homebrew,ralic/homebrew,kevinastone/homebrew,ablyler/homebrew,totalvoidness/homebrew,utzig/homebrew,3van/homebrew,marcwebbie/homebrew,menivaitsi/homebrew,tschoonj/homebrew,sjackman/linuxbrew,frodeaa/homebrew,LinusU/homebrew,cosmo0920/homebrew,eighthave/homebrew,cprecioso/homebrew,utzig/homebrew,ablyler/homebrew,skinny-framework/homebrew,johanhammar/homebrew,hongkongkiwi/homebrew,sjackman/linuxbrew,SteveClement/homebrew,pcottle/homebrew,utzig/homebrew,dalanmiller/homebrew,menivaitsi/homebrew,brunchboy/homebrew,alebcay/homebrew,scorphus/homebrew,Red54/homebrew,chadcatlett/homebrew,dunn/homebrew,haihappen/homebrew,ebouaziz/linuxbrew,afh/homebrew,slyphon/homebrew,youtux/homebrew,keith/homebrew,georgschoelly/homebrew,SuperNEMO-DBD/cadfaelbrew,ybott/homebrew,Red54/homebrew,apjanke/homebrew,DoomHammer/linuxbrew,MartinDelille/homebrew,dutchcoders/homebrew,retrography/homebrew,ralic/homebrew,ilovezfs/homebrew,osimola/homebrew,kenips/homebrew,hakamadare/homebrew,gicmo/homebrew,Homebrew/linuxbrew,dericed/homebrew,cscetbon/homebrew,TaylorMonacelli/homebrew,dickeyxxx/homebrew,treyharris/homebrew,treyharris/homebrew,OJFord/homebrew,reelsense/linuxbrew,saketkc/linuxbrew,sferik/homebrew,muellermartin/homebrew,royhodgman/homebrew,gnubila-france/linuxbrew,hakamadare/homebrew,polishgeeks/homebrew,esamson/homebrew,skatsuta/homebrew,menivaitsi/homebrew,dutchcoders/homebrew,gawbul/homebrew,osimola/homebrew,skinny-framework/homebrew,dalanmiller/homebrew,influxdb/homebrew,ear/homebrew,kodabb/homebrew,gicmo/homebrew,drewwells/homebrew,cscetbon/homebrew,mobileoverlord/homebrew-1,Homebrew/homebrew,scpeters/homebrew,theeternalsw0rd/homebrew,ralic/homebrew,bukzor/linuxbrew,nandub/homebrew,booi/homebrew,mkrapp/homebrew,Homebrew/linuxbrew,sferik/homebrew,galaxy001/homebrew,osimola/homebrew,gnubila-france/linuxbrew,reelsense/linuxbrew,drbenmorgan/linuxbrew,bigbes/homebrew,utzig/homebrew,brunchboy/homebrew,Homebrew/linuxbrew,quantumsteve/homebrew,ryanfb/homebrew,drbenmorgan/linuxbrew,thinker0/homebrew,totalvoidness/homebrew,elyscape/homebrew,treyharris/homebrew,jamer/homebrew,gnubila-france/linuxbrew,3van/homebrew,influxdata/homebrew,benjaminfrank/homebrew,getgauge/homebrew,esamson/homebrew,dunn/homebrew,menivaitsi/homebrew,base10/homebrew,DoomHammer/linuxbrew,afh/homebrew,Chilledheart/homebrew,BrewTestBot/homebrew,ear/homebrew,gnubila-france/linuxbrew,polishgeeks/homebrew,sakra/homebrew,frodeaa/homebrew,dalanmiller/homebrew,ExtremeMan/homebrew,elgertam/homebrew,elyscape/homebrew,michaKFromParis/homebrew-sparks,emcrisostomo/homebrew,elyscape/homebrew,skinny-framework/homebrew,josa42/homebrew,dplarson/homebrew,kevinastone/homebrew,mkrapp/homebrew,benjaminfrank/homebrew,elgertam/homebrew,theeternalsw0rd/homebrew,josa42/homebrew,tutumcloud/homebrew,redpen-cc/homebrew,frodeaa/homebrew,cosmo0920/homebrew,scpeters/homebrew,thinker0/homebrew,royhodgman/homebrew,hanxue/homebrew,georgschoelly/homebrew,reelsense/homebrew,johanhammar/homebrew,ilovezfs/homebrew,influxdb/homebrew,mobileoverlord/homebrew-1,saketkc/linuxbrew,BrewTestBot/homebrew,hanxue/homebrew,saketkc/linuxbrew,gicmo/homebrew,influxdata/homebrew,bukzor/linuxbrew,dutchcoders/homebrew,kenips/homebrew,dplarson/homebrew,haihappen/homebrew