Support the use case where GOPATH is a colon-separated list of paths
Support the use case where GOPATH is a colon-separated list of paths

Previously Makefile targets assume that ${GOPATH} contains a single path;
however, this is not the case esp. for Go Version Manager users.

Support this use case by defining ${GOPATH_1ST} to be the first path in
${GOPATH}, and using ${GOPATH_1ST} in the targets.

ikropotov/kops,andrewsykim/kops,sp-borja-juncosa/kops,luomiao/kops,ikropotov/kops,MadDogTechnology/kops,chrislovecnm/kops,chrislovecnm/kops,DualSpark/kops,WillemMali/kops,kris-nova/kops,WillemMali/kops,robinpercy/kops,BradErz/kops,reactiveops/kops,kubernetes/kops,mad01/kops,BradErz/kops,robinpercy/kops,sethpollack/kops,kris-nova/kops,zytek/kops,kris-nova/kops,andrewsykim/kops,austinmoore-/kops,dacohen/kops,leandrocr/kops,reactiveops/kops,kris-nova/kops,blakebarnett/kops,faraazkhan/kops,blakebarnett/kops,MadDogTechnology/kops,tsupertramp/kops,chrislovecnm/kops,aledbf/kops,reactiveops/kops,dacohen/kops,gambol99/kops,austinmoore-/kops,kubernetes/kops,zytek/kops,andrewsykim/kops,gambol99/kops,MadDogTechnology/kops,sethpollack/kops,sp-borja-juncosa/kops,austinmoore-/kops,luomiao/kops,robinpercy/kops,leandrocr/kops,justinsb/kops,tsupertramp/kops,BradErz/kops,austinmoore-/kops,BradErz/kops,ikropotov/kops,tsupertramp/kops,faraazkhan/kops,WillemMali/kops,WillemMali/kops,mad01/kops,jnewland/kops,pdh/kops,dacohen/kops,justinsb/kops,DualSpark/kops,blakebarnett/kops,leandrocr/kops,blakebarnett/kops,faraazkhan/kops,andrewsykim/kops,sethpollack/kops,jnewland/kops,aledbf/kops,zytek/kops,tsupertramp/kops,pdh/kops,luomiao/kops,aledbf/kops,gambol99/kops,mad01/kops,chrislovecnm/kops,faraazkhan/kops,sethpollack/kops,MadDogTechnology/kops,leandrocr/kops,jnewland/kops,justinsb/kops,aledbf/kops,sp-borja-juncosa/kops,pdh/kops,pdh/kops,ikropotov/kops,robinpercy/kops,DualSpark/kops,luomiao/kops,gambol99/kops,reactiveops/kops,zytek/kops,dacohen/kops,mad01/kops,sp-borja-juncosa/kops,kubernetes/kops,DualSpark/kops