go.tools/dashboard/builder: remove redundant makefile
go.tools/dashboard/builder: remove redundant makefile

LGTM=adg
R=adg
CC=golang-codereviews
https://golang.org/cl/95410043

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