Use named volumes for docker pkg cache
Use named volumes for docker pkg cache

Changes the default when incremental build is enabled to use named
volumes instead of bindmounts.
The reason for this is, on Mac/Windows the bind mounts will go over the
shared fs, which is incredibly slow and itself uses lots of CPU.

Makes an incremental build on OSX go from ~40s to 10s.

To get the old behavior, can set `PKGCACHE_DIR=.go-pkg-cache`

Signed-off-by: Brian Goff <dc73d0991b982a8303e713ef531a313af77e242a@gmail.com>

shhsu/docker,moul/docker,mikedougherty/docker,moul/docker,konstruktoid/docker-upstream,Syntaxide/docker,mike1729/docker,mahak/docker,qudongfang/docker,bearstech/moby,ibuildthecloud/docker,KarthikNayak/docker,jimjag/docker,yongtang/docker,laijs/docker,gjaskiewicz/moby,dims/docker,laijs/docker,prertik/docker,vdemeester/docker,flavio/docker,konstruktoid/docker-1,tophj-ibm/docker,POLJM242/docker,johnstep/moby-moby,duglin/docker,thaJeztah/docker,srust/docker,kolyshkin/docker,coolljt0725/docker,bonczj/moby-json-file-logger,mikedougherty/docker,kojiromike/docker,tklauser/docker,yasiramin10p/moby,ffoysal/docker,tophj-ibm/docker,KarthikNayak/docker,flavio/docker,thaJeztah/docker,rancher/docker,darrenstahlmsft/docker,docker/docker,konstruktoid/docker-upstream,kolyshkin/moby,flavio/docker,AkihiroSuda/docker,unclejack/docker,darrenstahlmsft/docker,shishir-a412ed/docker,madhanrm/docker,laijs/moby,trebonian/docker,dims/docker,alfred-landrum/docker,thaJeztah/docker,ripcurld0/moby,johnstep/moby-moby,AkihiroSuda/docker,sterchelen/docker,whuwxl/docker,gjaskiewicz/moby,cpuguy83/docker,djs55/docker,moypray/docker,jwhonce/docker,KingEmet/docker,amatsus/docker,mstanleyjones/docker,ibuildthecloud/docker,cpuguy83/docker,michael-holzheu/docker,bearstech/moby,mkumatag/docker,dccurtis/docker,allencloud/docker,akira-baruah/docker,lixiaobing1/docker,tmp6154/docker,michael-holzheu/docker,whuwxl/docker,lixiaobing10051267/docker,HideoYamauchi/docker,resin-io/docker,raja-sami-10p/moby,fcrisciani/docker,mikebrow/docker,jwhonce/docker,rhatdan/docker,tophj-ibm/moby,madhanrm/docker,docker/docker,moby/moby,liaoqingwei/docker,yummypeng/docker,erikh/docker,ffoysal/docker,yosifkit/docker,dccurtis/docker,dgageot/docker,harche/docker,bonczj/moby-json-file-logger,imkin/moby,noironetworks/docker,thaJeztah/docker,pramodhkp/moby,miminar/docker,resin-io/docker,pradipd/moby,akira-baruah/docker,harche/docker,danyalKhaliq10p/moby,mixja/docker,yongtang/docker,nawawi/docker,allencloud/docker,erikstmartin/docker,danyalKhaliq10p/moby,liaoqingwei/docker,dmcgowan/docker,catinthesky/docker,shishir-a412ed/docker,paralin/docker,erikstmartin/docker,dsheets/moby,bearstech/moby,mtesselH/docker,estesp/docker,trebonian/docker,moypray/docker,jvanz/docker,catinthesky/docker,rremer/moby,JMesser81/docker,ColinHebert/docker,sterchelen/docker,mahak/docker,naveed-jamil-tenpearls/moby,Ramzec/docker,hqhq/moby,yosifkit/docker,hqhq/moby,rancher/docker,KingEmet/docker,mixja/docker,miminar/docker,dgageot/docker,dmcgowan/docker,qudongfang/docker,paralin/docker,rremer/moby,harche/docker,yasiramin10p/moby,mikebrow/docker,yongtang/docker,PatrickLang/moby,q384566678/docker,pradipd/moby,lixiaobing1/docker,djs55/docker,ndeloof/docker,nalind/docker,mikebrow/docker,KarthikNayak/docker,vdemeester/docker,haveatry/docker,konstruktoid/docker-1,JMesser81/docker,amatsus/docker,kencochrane/docker,q384566678/docker,pramodhkp/moby,x1022as/docker,trebonian/docker,x1022as/docker,lixiaobing10051267/docker,charleszheng44/moby,rhatdan/docker,lixiaobing10051267/docker,nawawi/docker,diogomonica/docker,coreos/docker,lixiaobing1/docker,rhatdan/docker,srust/docker,sarnautov/moby,nalind/docker,charleszheng44/moby,gjaskiewicz/moby,darrenstahlmsft/moby,naveed-jamil-tenpearls/moby,mahak/docker,erikh/docker,ripcurld0/moby,diogomonica/docker,kencochrane/docker,diogomonica/docker,YuPengZTE/docker,kolyshkin/docker,fcrisciani/docker,trebonian/docker,dperny/docker,tonistiigi/docker,dperny/docker,coolljt0725/docker,cyphar/docker,dsheets/moby,mike1729/docker,laijs/moby,YuPengZTE/docker,rancher/docker,tonistiigi/docker,shishir-a412ed/docker,JMesser81/docker,haveatry/docker,tianon/docker,paralin/docker,gnailuy/docker,dims/docker,raja-sami-10p/moby,sterchelen/docker,sarnautov/moby,rremer/moby,sdurrheimer/docker,jthelin/docker,mstanleyjones/docker,jlhawn/docker,mike1729/docker,Mokolea/docker,scotttlin/docker,raja-sami-10p/moby,Mokolea/docker,konstruktoid/docker-upstream,kojiromike/docker,bearstech/moby,maxamillion/docker,hqhq/moby,tonistiigi/docker,maxamillion/docker,tklauser/docker,coreos/docker,tophj-ibm/moby,alfred-landrum/docker,sdurrheimer/docker,noironetworks/docker,liaoqingwei/docker,Mokolea/docker,POLJM242/docker,x1022as/docker,thtanaka/docker,SvenDowideit/docker,vdemeester/docker,naveed-jamil-tenpearls/moby,fcrisciani/docker,miminar/docker,mtesselH/docker,prertik/docker,tmp6154/docker,mkumatag/docker,ripcurld0/moby,xuxinkun/docker,mikedougherty/docker,jthelin/docker,cpuguy83/docker,johnstep/moby-moby,ibuildthecloud/docker,PatrickLang/moby,darrenstahlmsft/moby,crosbymichael/docker,q384566678/docker,flavio/docker,charleszheng44/moby,justincormack/docker,yummypeng/docker,moul/docker,resin-io/docker,estesp/docker,imkin/moby,estesp/docker,darrenstahlmsft/docker,ColinHebert/docker,scotttlin/docker,coolljt0725/docker,gnailuy/docker,moul/docker,paralin/docker,crosbymichael/docker,Ramzec/docker,SvenDowideit/docker,scotttlin/docker,duglin/docker,tophj-ibm/moby,shhsu/docker,kojiromike/docker,maxamillion/docker,laijs/moby,erikh/docker,jlhawn/docker,tklauser/docker,imkin/moby,nawawi/docker,dperny/docker,prertik/docker,laijs/docker,erikstmartin/docker,mixja/docker,jimjag/docker,bonczj/moby-json-file-logger,tophj-ibm/docker,cyphar/docker,Mokolea/docker,kolyshkin/moby,gnailuy/docker,YuPengZTE/docker,noironetworks/docker,sdurrheimer/docker,whuwxl/docker,unclejack/docker,dsheets/moby,duglin/docker,ColinHebert/docker,nawawi/docker,dmcgowan/docker,jameszhan/docker,kencochrane/docker,AkihiroSuda/docker,michael-holzheu/docker,jameszhan/docker,KingEmet/docker,HideoYamauchi/docker,nalind/docker,sarnautov/moby,ibuildthecloud/docker,allencloud/docker,pradipd/moby,ndeloof/docker,qudongfang/docker,Ramzec/docker,dccurtis/docker,cpuguy83/docker,tmp6154/docker,yosifkit/docker,ndeloof/docker,cyphar/docker,xuxinkun/docker,tianon/docker,PatrickLang/moby,unclejack/docker,moypray/docker,amatsus/docker,catinthesky/docker,xuxinkun/docker,ffoysal/docker,docker/docker,moby/moby,haveatry/docker,kolyshkin/moby,jameszhan/docker,ibuildthecloud/docker,jimjag/docker,AkihiroSuda/docker,konstruktoid/docker-1,yosifkit/docker,djs55/docker,gnailuy/docker,pramodhkp/moby,shhsu/docker,yummypeng/docker,darrenstahlmsft/moby,crosbymichael/docker,yasiramin10p/moby,jvanz/docker,SvenDowideit/docker,Syntaxide/docker,srust/docker,mtesselH/docker,jvanz/docker,thtanaka/docker,danyalKhaliq10p/moby,dgageot/docker,coreos/docker,madhanrm/docker,jwhonce/docker,thtanaka/docker,nalind/docker,mahak/docker,mstanleyjones/docker,Ramzec/docker,gschaetz/moby,moby/moby,gschaetz/moby,justincormack/docker,moby/moby,jimjag/docker,Syntaxide/docker,mkumatag/docker,jlhawn/docker,konstruktoid/docker-upstream,justincormack/docker,gschaetz/moby,alfred-landrum/docker,HideoYamauchi/docker