Add 'backup-rust' and 'restore-rust' build targets
Add 'backup-rust' and 'restore-rust' build targets

backup-rust moves src/rust up, out of the build directory and restore-rust
moves it back. For use by build automation.

pyecs/servo,anthgur/servo,s142857/servo,DominoTree/servo,g-k/servo,nrc/servo,caldwell/servo,owaspjocur/servo,larsbergstrom/servo,chotchki/servo,dagnir/servo,rixrix/servo,dati91/servo,canaltinova/servo,s142857/servo,mrobinson/servo,tafia/servo,Shraddha512/servo,mukilan/servo,SimonSapin/servo,nerith/servo,paulrouget/servo,walac/servo,nick-thompson/servo,snf/servo,dvberkel/servo,wpgallih/servo,RenaudParis/servo,nnethercote/servo,indykish/servo,bhearsum-bors/servo,WriterOfAlicrow/servo,paulrouget/servo,karlito40/servo,rentongzhang/servo,snf/servo,aweinstock314/servo,huonw/servo,ryancanhelpyou/servo,cbrewster/servo,GyrosOfWar/servo,canaltinova/servo,meh/servo,jimberlage/servo,szeged/servo,tempbottle/servo,splav/servo,indykish/servo,szeged/servo,saneyuki/servo,dsandeephegde/servo,dvberkel/servo,boghison/servo,DominoTree/servo,codemac/servo,michaelwu/servo,dsandeephegde/servo,froydnj/servo,bjwbell/servo,mattnenterprise/servo,CJ8664/servo,juzer10/servo,hyowon/servo,deokjinkim/servo,eddyb/servo,dhananjay92/servo,chotchki/servo,sadmansk/servo,dmarcos/servo,KiChjang/servo,chotchki/servo,saneyuki/servo,upsuper/servo,Adenilson/prototype-viewing-distance,tafia/servo,pyecs/servo,wpgallih/servo,owaspjocur/servo,zentner-kyle/servo,karlito40/servo,shrenikgala/servo,hyowon/servo,bhearsum-bors/servo,youprofit/servo,GyrosOfWar/servo,DominoTree/servo,notriddle/servo,emilio/servo,sadmansk/servo,GyrosOfWar/servo,thiagopnts/servo,RenaudParis/servo,kindersung/servo,j3parker/servo,meh/servo,kindersung/servo,zentner-kyle/servo,ConnorGBrewster/servo,mattnenterprise/servo,GreenRecycleBin/servo,rentongzhang/servo,cbrewster/servo,paulrouget/servo,GyrosOfWar/servo,pgonda/servo,nnethercote/servo,mrobinson/servo,caldwell/servo,mt2d2/servo,codemac/servo,shrenikgala/servo,zhangjunlei26/servo,tafia/servo,owaspjocur/servo,paulrouget/servo,boghison/servo,zentner-kyle/servo,peterjoel/servo,thiagopnts/servo,kindersung/servo,nnethercote/servo,anthgur/servo,dagnir/servo,DominoTree/servo,Shraddha512/servo,j3parker/servo,samfoo/servo,GreenRecycleBin/servo,upsuper/servo,pyecs/servo,zhangjunlei26/servo,dagnir/servo,upsuper/servo,mdibaiee/servo,emilio/servo,Shraddha512/servo,avadacatavra/servo,aweinstock314/servo,larsbergstrom/servo,KiChjang/servo,pcwalton/servo,jimberlage/servo,samfoo/servo,jgraham/servo,brson/servo,huonw/servo,nrc/servo,shrenikgala/servo,jlegendary/servo,metajack/servo,steveklabnik/servo,mukilan/servo,cbrewster/servo,chotchki/servo,dsandeephegde/servo,zentner-kyle/servo,seanmonstar/servo,rnestler/servo,boghison/servo,zhangjunlei26/servo,g-k/servo,pyfisch/servo,walac/servo,evilpie/servo,cbrewster/servo,emilio/servo,wartman4404/servo,nrc/servo,boghison/servo,tschneidereit/servo,bjwbell/servo,juzer10/servo,A-deLuna/servo,DominoTree/servo,j3parker/servo,RenaudParis/servo,paulrouget/servo,mt2d2/servo,WriterOfAlicrow/servo,nnethercote/servo,KiChjang/servo,codemac/servo,szeged/servo,sadmansk/servo,dati91/servo,nrc/servo,mdibaiee/servo,mattnenterprise/servo,tempbottle/servo,wpgallih/servo,mbrubeck/servo,brendandahl/servo,caldwell/servo,evilpie/servo,RenaudParis/servo,samfoo/servo,jimberlage/servo,deokjinkim/servo,brson/servo,thiagopnts/servo,aidanhs/servo,rixrix/servo,zhangjunlei26/servo,bfrohs/servo,nrc/servo,deokjinkim/servo,luniv/servo,GyrosOfWar/servo,Adenilson/prototype-viewing-distance,tempbottle/servo,szeged/servo,CJ8664/servo,pgonda/servo,splav/servo,peterjoel/servo,bfrohs/servo,owaspjocur/servo,bhearsum-bors/servo,s142857/servo,codemac/servo,jlegendary/servo,jlegendary/servo,nerith/servo,ruud-v-a/servo,mukilan/servo,cbrewster/servo,evilpie/servo,dhananjay92/servo,indykish/servo,notriddle/servo,pgonda/servo,SimonSapin/servo,canaltinova/servo,paulrouget/servo,bjwbell/servo,Aalhad/CanvasRenderingContext2DMozilla,metajack/servo,KiChjang/servo,echochamber/servo,KiChjang/servo,hyowon/servo,ConnorGBrewster/servo,mrobinson/servo,KiChjang/servo,meh/servo,fiji-flo/servo,anthgur/servo,jlegendary/servo,jimberlage/servo,ruud-v-a/servo,echochamber/servo,caldwell/servo,splav/servo,brson/servo,SimonSapin/servo,rnestler/servo,notriddle/servo,eddyb/servo,notriddle/servo,jimberlage/servo,dvberkel/servo,WriterOfAlicrow/servo,saratang/servo,jgraham/servo,runarberg/servo,jgraham/servo,GreenRecycleBin/servo,RenaudParis/servo,DominoTree/servo,pcwalton/servo,upsuper/servo,akosel/servo,AnthonyBroadCrawford/servo,splav/servo,Adenilson/prototype-viewing-distance,seanmonstar/servo,ConnorGBrewster/servo,ruud-v-a/servo,codemac/servo,kindersung/servo,huonw/servo,nnethercote/servo,bhearsum-bors/servo,brendandahl/servo,juzer10/servo,s142857/servo,michaelwu/servo,brendandahl/servo,mukilan/servo,DominoTree/servo,steveklabnik/servo,mbrubeck/servo,nnethercote/servo,szeged/servo,anthgur/servo,bjwbell/servo,peterjoel/servo,peterjoel/servo,huonw/servo,srbhklkrn/SERVOENGINE,aidanhs/servo,youprofit/servo,s142857/servo,evilpie/servo,anthgur/servo,emilio/servo,jlegendary/servo,echochamber/servo,deokjinkim/servo,saneyuki/servo,pyecs/servo,larsbergstrom/servo,vks/servo,aweinstock314/servo,larsbergstrom/servo,saneyuki/servo,saratang/servo,deokjinkim/servo,pgonda/servo,indykish/servo,szeged/servo,rixrix/servo,saneyuki/servo,SimonSapin/servo,snf/servo,thiagopnts/servo,pgonda/servo,Shraddha512/servo,nnethercote/servo,sadmansk/servo,SimonSapin/servo,hyowon/servo,pyfisch/servo,pyecs/servo,CJ8664/servo,wpgallih/servo,j3parker/servo,boghison/servo,karlito40/servo,ryancanhelpyou/servo,bhearsum-bors/servo,larsbergstrom/servo,emilio/servo,Aalhad/CanvasRenderingContext2DMozilla,dmarcos/servo,larsbergstrom/servo,rentongzhang/servo,srbhklkrn/SERVOENGINE,luniv/servo,hyowon/servo,Adenilson/prototype-viewing-distance,aweinstock314/servo,nerith/servo,shrenikgala/servo,g-k/servo,RenaudParis/servo,A-deLuna/servo,mbrubeck/servo,walac/servo,KiChjang/servo,nrc/servo,metajack/servo,KiChjang/servo,metajack/servo,aweinstock314/servo,boghison/servo,g-k/servo,runarberg/servo,samfoo/servo,mdibaiee/servo,paulrouget/servo,anthgur/servo,karlito40/servo,indykish/servo,juzer10/servo,fiji-flo/servo,emilio/servo,thiagopnts/servo,evilpie/servo,pyfisch/servo,snf/servo,jdramani/servo,wartman4404/servo,sadmansk/servo,dhananjay92/servo,larsbergstrom/servo,sadmansk/servo,pyfisch/servo,saneyuki/servo,splav/servo,dhananjay92/servo,cbrewster/servo,CJ8664/servo,michaelwu/servo,froydnj/servo,nick-thompson/servo,pyecs/servo,nnethercote/servo,deokjinkim/servo,nrc/servo,pyfisch/servo,walac/servo,rnestler/servo,mdibaiee/servo,eddyb/servo,shrenikgala/servo,tschneidereit/servo,brson/servo,tempbottle/servo,eddyb/servo,rixrix/servo,DominoTree/servo,jgraham/servo,youprofit/servo,A-deLuna/servo,splav/servo,huonw/servo,caldwell/servo,dvberkel/servo,bhearsum-bors/servo,splav/servo,dati91/servo,ConnorGBrewster/servo,michaelwu/servo,echochamber/servo,tschneidereit/servo,CJ8664/servo,snf/servo,Shraddha512/servo,wpgallih/servo,brendandahl/servo,youprofit/servo,rixrix/servo,samfoo/servo,saratang/servo,indykish/servo,fiji-flo/servo,meh/servo,seanmonstar/servo,ConnorGBrewster/servo,youprofit/servo,mt2d2/servo,jimberlage/servo,meh/servo,splav/servo,aweinstock314/servo,Adenilson/prototype-viewing-distance,rentongzhang/servo,shrenikgala/servo,kindersung/servo,nick-thompson/servo,nerith/servo,bfrohs/servo,upsuper/servo,szeged/servo,zentner-kyle/servo,larsbergstrom/servo,dsandeephegde/servo,juzer10/servo,peterjoel/servo,tschneidereit/servo,dati91/servo,dmarcos/servo,jdramani/servo,mattnenterprise/servo,jlegendary/servo,WriterOfAlicrow/servo,jimberlage/servo,notriddle/servo,mt2d2/servo,snf/servo,zhangjunlei26/servo,runarberg/servo,bfrohs/servo,emilio/servo,notriddle/servo,runarberg/servo,CJ8664/servo,vks/servo,avadacatavra/servo,nnethercote/servo,jgraham/servo,dsandeephegde/servo,jdramani/servo,boghison/servo,dagnir/servo,tafia/servo,huonw/servo,avadacatavra/servo,ConnorGBrewster/servo,srbhklkrn/SERVOENGINE,dmarcos/servo,rixrix/servo,akosel/servo,vks/servo,peterjoel/servo,seanmonstar/servo,avadacatavra/servo,brson/servo,runarberg/servo,mt2d2/servo,GreenRecycleBin/servo,notriddle/servo,dati91/servo,mrobinson/servo,dmarcos/servo,pcwalton/servo,rentongzhang/servo,canaltinova/servo,mbrubeck/servo,emilio/servo,peterjoel/servo,aidanhs/servo,ryancanhelpyou/servo,meh/servo,froydnj/servo,sadmansk/servo,luniv/servo,anthgur/servo,upsuper/servo,g-k/servo,AnthonyBroadCrawford/servo,echochamber/servo,akosel/servo,hyowon/servo,dvberkel/servo,s142857/servo,brson/servo,caldwell/servo,metajack/servo,jdramani/servo,dati91/servo,zentner-kyle/servo,mbrubeck/servo,AnthonyBroadCrawford/servo,RenaudParis/servo,mattnenterprise/servo,walac/servo,DominoTree/servo,SimonSapin/servo,juzer10/servo,luniv/servo,vks/servo,mdibaiee/servo,brendandahl/servo,wartman4404/servo,aidanhs/servo,jimberlage/servo,A-deLuna/servo,Aalhad/CanvasRenderingContext2DMozilla,anthgur/servo,aidanhs/servo,Aalhad/CanvasRenderingContext2DMozilla,pcwalton/servo,CJ8664/servo,thiagopnts/servo,rnestler/servo,bfrohs/servo,froydnj/servo,pcwalton/servo,DominoTree/servo,A-deLuna/servo,szeged/servo,bfrohs/servo,paulrouget/servo,walac/servo,luniv/servo,thiagopnts/servo,emilio/servo,brendandahl/servo,karlito40/servo,wpgallih/servo,michaelwu/servo,nick-thompson/servo,snf/servo,juzer10/servo,pgonda/servo,notriddle/servo,tafia/servo,upsuper/servo,samfoo/servo,saneyuki/servo,SimonSapin/servo,kindersung/servo,dsandeephegde/servo,echochamber/servo,fiji-flo/servo,mattnenterprise/servo,ConnorGBrewster/servo,Aalhad/CanvasRenderingContext2DMozilla,saneyuki/servo,KiChjang/servo,WriterOfAlicrow/servo,Shraddha512/servo,g-k/servo,caldwell/servo,eddyb/servo,splav/servo,tafia/servo,deokjinkim/servo,mdibaiee/servo,szeged/servo,aidanhs/servo,notriddle/servo,walac/servo,evilpie/servo,hyowon/servo,GreenRecycleBin/servo,chotchki/servo,shrenikgala/servo,froydnj/servo,michaelwu/servo,saratang/servo,nick-thompson/servo,mdibaiee/servo,wartman4404/servo,wpgallih/servo,rixrix/servo,WriterOfAlicrow/servo,rnestler/servo,fiji-flo/servo,dvberkel/servo,runarberg/servo,akosel/servo,bjwbell/servo,rnestler/servo,szeged/servo,pcwalton/servo,ryancanhelpyou/servo,saratang/servo,saratang/servo,youprofit/servo,fiji-flo/servo,luniv/servo,eddyb/servo,A-deLuna/servo,nerith/servo,jgraham/servo,luniv/servo,kindersung/servo,zhangjunlei26/servo,dagnir/servo,s142857/servo,dagnir/servo,steveklabnik/servo,saneyuki/servo,mukilan/servo,notriddle/servo,karlito40/servo,Adenilson/prototype-viewing-distance,jimberlage/servo,wartman4404/servo,dati91/servo,bjwbell/servo,canaltinova/servo,dagnir/servo,A-deLuna/servo,codemac/servo,codemac/servo,akosel/servo,vks/servo,jdramani/servo,rnestler/servo,g-k/servo,srbhklkrn/SERVOENGINE,saratang/servo,j3parker/servo,paulrouget/servo,evilpie/servo,dhananjay92/servo,eddyb/servo,indykish/servo,samfoo/servo,steveklabnik/servo,SimonSapin/servo,mt2d2/servo,wpgallih/servo,splav/servo,huonw/servo,dvberkel/servo,thiagopnts/servo,canaltinova/servo,wartman4404/servo,ruud-v-a/servo,Shraddha512/servo,dmarcos/servo,dhananjay92/servo,wartman4404/servo,echochamber/servo,j3parker/servo,paulrouget/servo,brendandahl/servo,seanmonstar/servo,CJ8664/servo,fiji-flo/servo,tschneidereit/servo,mt2d2/servo,mbrubeck/servo,avadacatavra/servo,steveklabnik/servo,owaspjocur/servo,bjwbell/servo,wpgallih/servo,AnthonyBroadCrawford/servo,metajack/servo,ryancanhelpyou/servo,peterjoel/servo,tafia/servo,jgraham/servo,zhangjunlei26/servo,rnestler/servo,jlegendary/servo,AnthonyBroadCrawford/servo,evilpie/servo,Adenilson/prototype-viewing-distance,eddyb/servo,chotchki/servo,mbrubeck/servo,pyecs/servo,rixrix/servo,youprofit/servo,ruud-v-a/servo,mrobinson/servo,mattnenterprise/servo,rentongzhang/servo,tempbottle/servo,avadacatavra/servo,zhangjunlei26/servo,pyfisch/servo,aweinstock314/servo,nick-thompson/servo,srbhklkrn/SERVOENGINE,peterjoel/servo,pyfisch/servo,GyrosOfWar/servo,rentongzhang/servo,avadacatavra/servo,larsbergstrom/servo,aidanhs/servo,akosel/servo,ConnorGBrewster/servo,GreenRecycleBin/servo,mukilan/servo,cbrewster/servo,rixrix/servo,steveklabnik/servo,runarberg/servo,AnthonyBroadCrawford/servo,jdramani/servo,GyrosOfWar/servo,srbhklkrn/SERVOENGINE,dati91/servo,evilpie/servo,nick-thompson/servo,GreenRecycleBin/servo,GreenRecycleBin/servo,nerith/servo,canaltinova/servo,zhangjunlei26/servo,pyfisch/servo,cbrewster/servo,dsandeephegde/servo,ryancanhelpyou/servo,sadmansk/servo,meh/servo,pgonda/servo,emilio/servo,dhananjay92/servo,nnethercote/servo,KiChjang/servo,mrobinson/servo,Aalhad/CanvasRenderingContext2DMozilla,saneyuki/servo,tempbottle/servo,indykish/servo,j3parker/servo,canaltinova/servo,srbhklkrn/SERVOENGINE,dsandeephegde/servo,larsbergstrom/servo,vks/servo,karlito40/servo,vks/servo,ryancanhelpyou/servo,ruud-v-a/servo,GreenRecycleBin/servo,nerith/servo,zentner-kyle/servo,mbrubeck/servo,peterjoel/servo,owaspjocur/servo,AnthonyBroadCrawford/servo,pyfisch/servo,upsuper/servo,froydnj/servo,pyfisch/servo,seanmonstar/servo,tempbottle/servo,avadacatavra/servo,fiji-flo/servo,mattnenterprise/servo,dmarcos/servo,steveklabnik/servo,jdramani/servo,tschneidereit/servo,indykish/servo,tschneidereit/servo,akosel/servo,WriterOfAlicrow/servo