go.tools/dashboard: clone main repo from local path if it already exists locally.
go.tools/dashboard: clone main repo from local path if it already exists locally.

R=adg, minux.ma
CC=golang-dev
https://golang.org/cl/14462049

syreclabs/go-tools,jdhenke/tools,josharian/tools,springning/tools,dmitris/tools,matryer/tools,matryer/tools,nicot/tools,cw2018/tools,4ad/tools,cmars/tools,josharian/tools,argandas/tools,springning/tools,cmars/tools,maddyonline/tools,argandas/tools,syreclabs/go-tools,argandas/tools,sshetty10/tools,jdhenke/tools,sshetty10/tools,jdhenke/tools,matryer/tools,maddyonline/tools,golang/tools,runcom/tools,cmars/tools,golang/tools,syreclabs/go-tools,matryer/tools,springning/tools,nicot/tools,glasser/golang-tools,magiccao/tools,runcom/tools,josharian/tools,dmitris/tools,cmars/tools,syreclabs/go-tools,magiccao/tools,argandas/tools,sshetty10/tools,4ad/tools,dmitris/tools,golang/tools,golang/tools,dmitris/tools,glasser/golang-tools,glasser/golang-tools,nicot/tools,sshetty10/tools,magiccao/tools,josharian/tools,syreclabs/go-tools,nicot/tools,syreclabs/go-tools,springning/tools,4ad/tools,cw2018/tools,golang/tools,cw2018/tools,runcom/tools,maddyonline/tools,jdhenke/tools,runcom/tools,glasser/golang-tools,cw2018/tools,magiccao/tools,maddyonline/tools