Add ability to send log output to a file
Add ability to send log output to a file

Using PACKER_LOG=1 causes all the log output to be sent to Stderr. This
change maintains that backward compatility. Anything other than "1" will
be treated as a filename which will have logging appended to that file.
This is useful, for example, to always have debugging available without
cluttering up stdout (and without having to redirect stderr all the time).

ephemeralsnow/packer,tas50/packer,hashicorp/packer,sean-/packer,timsutton/packer,yoctocloud/packer,mwhooker/packer,zakuro9715/packer,mitchellh/packer,beni55/packer,life360/packer,lantrix/packer,lantrix/packer,ttaylor249/packer,visioncritical/packer,Cbeck527/packer,jarl-dk/packer,danschaffer/packer,threatstream/packer,ttaylor249/packer,dev-head/packer,dantran/packer,quantang/packer,tracyde/packer,evertrue/packer,vtolstov/packer,KFishner/packer,dev-head/packer,quantang/packer,LinusU/packer,zhuzhih2017/packer,gbarberi/packer,timsutton/packer,rodm/packer,Banno/packer,hasJackb/packer,uber/packer,cyberhouse/packer,jen20/packer,kpettijohn/packer,tsmolka/packer,c22/packer,sean-/packer,pvandervelde/packer,jonathankarsh/packer,life360/packer,jsternberg/packer,mohae/packer,grubernaut/packer,hasJackb/packer,ldejager/packer,mkuzmin/packer,pvanbuijtene/packer,oliviertremblay/packer,bensojona/packer,jszwedko/packer,arizvisa/packer,pearkes/packer,zeliff/packer,bensojona/packer,boumenot/packer,atlassian/packer,tas50/packer,rnaveiras/packer,grange74/packer,justincampbell/packer,fnoeding/packer,tas50/packer,monkeylittleinc/packer,p1-nico/packer,pecigonzalo/packer,pearkes/packer,jae2/packer,visioncritical/packer,evertrue/packer,napramirez/packer,dantran/packer,mefellows/packer,p1-nico/packer,ChrisLundquist/packer,israelshirk/packer,mefellows/packer,jgkim/packer,paulmey/packer,c22/packer,jsternberg/packer,uber/packer,routelastresort/packer,ober/packer,tas50/packer,justincampbell/packer,c22/packer,vtolstov/packer,jean/packer,grubernaut/packer,sobrinho/packer,leroux/packer,KohlsTechnology/packer,uber/packer,jae2/packer,arizvisa/packer,umang1912/packer,jamesbishopp/packer,jamesbishopp/packer,sequenceiq/packer,oliviertremblay/packer,Banno/packer,hasJackb/packer,aneeshusa/packer,jmptrader/packer,blairham/packer,routelastresort/packer,arizvisa/packer,BayanGroup/packer,aneeshusa/packer,monsterzz/packer,c22/packer,zhuzhih2017/packer,icnocop/packer,icnocop/packer,umang1912/packer,routelastresort/packer,gildas/packer-hyperv,visioncritical/packer,sansb/packer,feateds/packer,mkuzmin/packer,pvandervelde/packer,ttaylor249/packer,life360/packer,mafrosis/packer,dieu/packer,ldejager/packer,ricardclau/packer,Banno/packer,esemplare/packer,BayanGroup/packer,mayflower/packer,mefellows/packer,markpeek/packer,timsutton/packer,mayflower/packer,tsmolka/packer,jen20/packer,lantrix/packer,jszwedko/packer,markpeek/packer,tomwilkie/packer,leroux/packer,sean-/packer,boumenot/packer,taliesins/packer,DualSpark/packer,jean/packer,KohlsTechnology/packer,ober/packer,monkeylittleinc/packer,mansunkuo/packer,rickard-von-essen/packer,jamesleech/packer,jean/packer,KohlsTechnology/packer,jgkim/packer,dayglojesus/packer,jsoriano/packer,dayglojesus/packer,blairham/packer,dantran/packer,higebu/packer,p1-nico/packer,sansb/packer,youhong316/packer,burnzy/packer,higebu/packer,smaato/packer,danschaffer/packer,paulmey/packer,visioncritical/packer,tas50/packer,taliesins/packer,pvandervelde/packer,sgirones/packer,boumenot/packer,bensojona/packer,quantang/packer,btd/packer,btd/packer,atlassian/packer,israelshirk/packer,bradparks/packer__create_vm_for_aws_docker_vagrant_etc,Sheile/packer,AlphaStaxLLC/packer,masbog/packer,shaunduncan/packer,ChrisLundquist/packer,dragon788/packer,pearkes/packer,marklap/packer,legal90/packer,sobrinho/packer,jasonchaffee/packer,jmptrader/packer,hashicorp/packer,rk295/packer,pecigonzalo/packer,rk295/packer,eranchetz/packer,youhong316/packer,mitchellh/packer,paulvollmer/packer,ttaylor249/packer,mgk/packer,mohae/packer,umang1912/packer,AlphaStaxLLC/packer,oliviertremblay/packer,hasJackb/packer,atlassian/packer,Xiol/packer,esemplare/packer,ephemeralsnow/packer,avldya/packer,pvanbuijtene/packer,mwhooker/packer,mayflower/packer,jen20/packer,pvandervelde/packer,ricardclau/packer,oliviertremblay/packer,mansunkuo/packer,paulvollmer/packer,jimmythedog/packer,dave2/packer,ldejager/packer,esemplare/packer,bryson/packer,sequenceiq/packer,henrysher/packer,esemplare/packer,orivej/packer,tas50/packer,mefellows/packer,pvanbuijtene/packer,ttaylor249/packer,youhong316/packer,sneal/packer,pvanbuijtene/packer,ricardclau/packer,rrva/packer,samdunne/packer,mvanholsteijn/packer,mitchellh/packer,marc-ta/packer,eranchetz/packer,DualSpark/packer,hashicorp/packer,dragon788/packer,jamesbishopp/packer,tracyde/packer,Akasurde/packer,tsmolka/packer,mindjiver/packer,sean-/packer,ChrisLundquist/packer,beni55/packer,marc-ta/packer,grubernaut/packer,yonglehou/packer,smaato/packer,dragon788/packer,israelshirk/packer,youhong316/packer,legal90/packer,manicai/packer,feateds/packer,arizvisa/packer,henrysher/packer,mgk/packer,sansb/packer,zhuzhih2017/packer,sgirones/packer,monsterzz/packer,mindjiver/packer,grange74/packer,Silver90/packer,dave2/packer,tracyde/packer,quantang/packer,sneal/packer,eranchetz/packer,smaato/packer,beni55/packer,vtolstov/packer,bhcleek/packer,sobrinho/packer,kpettijohn/packer,bhcleek/packer,paulmey/packer,napramirez/packer,tb3088/packer,noplay/packer,Akasurde/packer,bryson/packer,pvandervelde/packer,ober/packer,ober/packer,mwhooker/packer,smaato/packer,DualSpark/packer,samdunne/packer,sneal/packer,qur/packer,jamesbishopp/packer,stagrlee/packer,yoctocloud/packer,eranchetz/packer,Xiol/packer,noplay/packer,higebu/packer,tb3088/packer,jonathankarsh/packer,rickard-von-essen/packer,napramirez/packer,jonathankarsh/packer,leroux/packer,ChrisLundquist/packer,KFishner/packer,mvanholsteijn/packer,tb3088/packer,LinusU/packer,gbarberi/packer,p1-nico/packer,israelshirk/packer,Akasurde/packer,beni55/packer,qur/packer,pvandervelde/packer,samdunne/packer,vtolstov/packer,aneeshusa/packer,marklap/packer,grange74/packer,icnocop/packer,boumenot/packer,yonglehou/packer,kgrvamsi/packer,jae2/packer,dragon788/packer,burnzy/packer,BayanGroup/packer,dantran/packer,napramirez/packer,mvanholsteijn/packer,burnzy/packer,jasonchaffee/packer,sneal/packer,masbog/packer,styro/packer,rk295/packer,higebu/packer,mitchellh/packer,tomwilkie/packer,DualSpark/packer,tomwilkie/packer,ldejager/packer,arizvisa/packer,jamesleech/packer,kgrvamsi/packer,ricardclau/packer,orivej/packer,Akasurde/packer,quantang/packer,pieter-lazzaro/packer,marklap/packer,jimmythedog/packer,ChrisLundquist/packer,marc-ta/packer,grubernaut/packer,dantran/packer,shaunduncan/packer,justincampbell/packer,jszwedko/packer,atlassian/packer,dayglojesus/packer,styro/packer,grange74/packer,ricardclau/packer,hazelesque/packer,jamesleech/packer,icnocop/packer,mindjiver/packer,zhuzhih2017/packer,bhcleek/packer,jamesleech/packer,icnocop/packer,ephemeralsnow/packer,bryson/packer,mafrosis/packer,mitchellh/packer,LinusU/packer,mindjiver/packer,yoctocloud/packer,henrysher/packer,shaunduncan/packer,blairham/packer,ricardclau/packer,mkuzmin/packer,Cbeck527/packer,jasonchaffee/packer,grange74/packer,atlassian/packer,Silver90/packer,btd/packer,stagrlee/packer,mkuzmin/packer,markpeek/packer,paulmey/packer,smaato/packer,zeliff/packer,bensojona/packer,pecigonzalo/packer,avldya/packer,dieu/packer,Cbeck527/packer,bryson/packer,paulvollmer/packer,jsoriano/packer,gbarberi/packer,jen20/packer,bhcleek/packer,Sheile/packer,jsoriano/packer,markpeek/packer,Cbeck527/packer,higebu/packer,kgrvamsi/packer,masbog/packer,mvanholsteijn/packer,shaunduncan/packer,threatstream/packer,sequenceiq/packer,dev-head/packer,life360/packer,mwhooker/packer,danschaffer/packer,legal90/packer,fnoeding/packer,yoctocloud/packer,noplay/packer,zhuzhih2017/packer,jimmythedog/packer,jasonchaffee/packer,jmptrader/packer,tb3088/packer,gildas/packer-hyperv,taliesins/packer,henrysher/packer,rnaveiras/packer,evertrue/packer,fnoeding/packer,mayflower/packer,bryson/packer,mafrosis/packer,bryson/packer,taliesins/packer,bhcleek/packer,jae2/packer,styro/packer,ChrisLundquist/packer,rrva/packer,gildas/packer-hyperv,qur/packer,Silver90/packer,blairham/packer,threatstream/packer,dave2/packer,Sheile/packer,timsutton/packer,zakuro9715/packer,zeliff/packer,grubernaut/packer,yonglehou/packer,Sheile/packer,mafrosis/packer,BayanGroup/packer,marc-ta/packer,rodm/packer,rickard-von-essen/packer,paulmey/packer,burnzy/packer,hazelesque/packer,ephemeralsnow/packer,aneeshusa/packer,jmptrader/packer,evertrue/packer,KohlsTechnology/packer,uber/packer,monkeylittleinc/packer,bradparks/packer__create_vm_for_aws_docker_vagrant_etc,LinusU/packer,danschaffer/packer,cyberhouse/packer,rodm/packer,dayglojesus/packer,threatstream/packer,dev-head/packer,jsternberg/packer,AlphaStaxLLC/packer,youhong316/packer,monkeylittleinc/packer,cyberhouse/packer,dave2/packer,umang1912/packer,rodm/packer,sean-/packer,KFishner/packer,ober/packer,tsmolka/packer,bradparks/packer__create_vm_for_aws_docker_vagrant_etc,manicai/packer,mohae/packer,jszwedko/packer,trumant/packer,routelastresort/packer,stagrlee/packer,mansunkuo/packer,rk295/packer,dave2/packer,sgirones/packer,pieter-lazzaro/packer,smaato/packer,pvanbuijtene/packer,threatstream/packer,zakuro9715/packer,pieter-lazzaro/packer,jimmythedog/packer,pieter-lazzaro/packer,rrva/packer,yonglehou/packer,rickard-von-essen/packer,danschaffer/packer,stagrlee/packer,p1-nico/packer,c22/packer,orivej/packer,routelastresort/packer,masbog/packer,KohlsTechnology/packer,tsmolka/packer,hashicorp/packer,sgirones/packer,mgk/packer,monsterzz/packer,jgkim/packer,styro/packer,feateds/packer,yoctocloud/packer,jgkim/packer,sneal/packer,jean/packer,timsutton/packer,hazelesque/packer,kgrvamsi/packer,c22/packer,tb3088/packer,marklap/packer,dieu/packer,taliesins/packer,leroux/packer,AlphaStaxLLC/packer,legal90/packer,fnoeding/packer,kpettijohn/packer,sansb/packer,rnaveiras/packer,taliesins/packer,jsternberg/packer,zakuro9715/packer,zhuzhih2017/packer,youhong316/packer,kpettijohn/packer,Xiol/packer,sean-/packer,KohlsTechnology/packer,trumant/packer,orivej/packer,sequenceiq/packer,mansunkuo/packer,legal90/packer,boumenot/packer,grubernaut/packer,samdunne/packer,zeliff/packer,pieter-lazzaro/packer,dave2/packer,trumant/packer,gbarberi/packer,jen20/packer,jonathankarsh/packer,tomwilkie/packer,pearkes/packer,dieu/packer,noplay/packer,timsutton/packer,dayglojesus/packer,btd/packer,manicai/packer,jimmythedog/packer,gildas/packer-hyperv,rrva/packer,jsoriano/packer,jarl-dk/packer,monsterzz/packer,mafrosis/packer,rnaveiras/packer,markpeek/packer,mayflower/packer,markpeek/packer,mkuzmin/packer,rickard-von-essen/packer,KFishner/packer,cyberhouse/packer,feateds/packer,p1-nico/packer,paulmey/packer,ephemeralsnow/packer,mohae/packer,jarl-dk/packer,mohae/packer,mansunkuo/packer,Cbeck527/packer,Akasurde/packer,avldya/packer,tracyde/packer,tsmolka/packer,tb3088/packer,arizvisa/packer,lantrix/packer,esemplare/packer,monkeylittleinc/packer,rnaveiras/packer,vtolstov/packer,mwhooker/packer,rnaveiras/packer,life360/packer,jarl-dk/packer,atlassian/packer,hazelesque/packer,manicai/packer,pieter-lazzaro/packer,mkuzmin/packer,bradparks/packer__create_vm_for_aws_docker_vagrant_etc,pecigonzalo/packer,Silver90/packer,paulvollmer/packer,justincampbell/packer,jasonchaffee/packer,jen20/packer,Xiol/packer,trumant/packer,mgk/packer,samdunne/packer,qur/packer,sobrinho/packer,avldya/packer