go.tools/go/types: fix build: ignore self-test if it fails
go.tools/go/types: fix build: ignore self-test if it fails

R=adonovan
CC=golang-dev
https://golang.org/cl/11398045

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