cmd/buildlet/stage0: set linux-arm-scaleway resolv.conf to 8.8.8.8

Fixes golang/go#14997

Change-Id: I44d5390d72da12f9f6ed8b2f3f5ec8f8ab13799f
Reviewed-on: https://go-review.googlesource.com/21194
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

cmd/buildlet/stage0/Makefile

@@ -1,19 +1,25 @@
-buildlet-stage0.windows-amd64: stage0.go
-	GOOS=windows GOARCH=amd64 go build -o $@
-	cat $@ | (cd ../../upload && go run upload.go --public --cacheable=false go-builder-data/$@)
+usage: FORCE
+	# See targets in Makefile
+	exit 1
 
-buildlet-stage0.linux-arm-scaleway: stage0.go
-	GOOS=linux GOARCH=arm go build -o $@
-	cat $@ | (cd ../../upload && go run upload.go --public --cacheable=false go-builder-data/$@)
+FORCE:
+
+buildlet-stage0.windows-amd64: FORCE
+	go install golang.org/x/build/cmd/upload
+	upload --verbose --osarch=$@ --file=go:golang.org/x/build/cmd/buildlet/stage0 --public --cacheable=false go-builder-data/$@
+
+buildlet-stage0.linux-arm-scaleway: FORCE
+	go install golang.org/x/build/cmd/upload
+	upload --verbose --osarch=$@ --file=go:golang.org/x/build/cmd/buildlet/stage0 --public --cacheable=false go-builder-data/$@
 
 # No staging vs prod targets here, because this file gets baked into
 # the Docker layers on gcr.io (which do have staging vs prod names).
 # That is, this file on GCS is only used at "docker build"-time, not
 # during day-to-day builds.
-buildlet-stage0.linux-amd64-kube: stage0.go
-	GOOS=linux GOARCH=amd64 go build -o $@
-	cat $@ | (cd ../../upload && go run upload.go --public --cacheable=false go-builder-data/$@)
+buildlet-stage0.linux-amd64-kube: FORCE
+	go install golang.org/x/build/cmd/upload
+	upload --verbose --osarch=$@ --file=go:golang.org/x/build/cmd/buildlet/stage0 --public --cacheable=false go-builder-data/$@
 
-buildlet-stage0.linux-s390x: stage0.go
-	GOOS=linux GOARCH=s390x go build -o $@
-	cat $@ | (cd ../../upload && go run upload.go --public --cacheable=false go-builder-data/$@)
+buildlet-stage0.linux-s390x: FORCE
+	go install golang.org/x/build/cmd/upload
+	upload --verbose --osarch=$@ --file=go:golang.org/x/build/cmd/buildlet/stage0 --public --cacheable=false go-builder-data/$@

cmd/buildlet/stage0/stage0.go

@@ -11,6 +11,7 @@
 package main
 
 import (
+	"bytes"
 	"encoding/json"
 	"flag"
 	"fmt"
@@ -218,6 +219,7 @@ func initScaleway() {
 	initScalewaySwap()
 	initScalewayWorkdir()
 	initScalewayMeta()
+	initScalewayDNS()
 	initScalewayGo14()
 	log.Printf("Scaleway init complete; metadata is %+v", scalewayMeta)
 }
@@ -253,6 +255,20 @@ func initScalewayMeta() {
 	}
 }
 
+func initScalewayDNS() {
+	setFileContents("/etc/resolv.conf", []byte("nameserver 8.8.8.8\n"))
+}
+
+func setFileContents(file string, contents []byte) {
+	old, err := ioutil.ReadFile(file)
+	if err == nil && bytes.Equal(old, contents) {
+		return
+	}
+	if err := ioutil.WriteFile(file, contents, 0644); err != nil {
+		log.Fatal(err)
+	}
+}
+
 func initScalewaySwap() {
 	const swapFile = "/swapfile"
 	slurp, _ := ioutil.ReadFile("/proc/swaps")

cmd/upload/upload.go

@@ -145,6 +145,9 @@ func buildGoTarget() {
 	if *osarch != "" {
 		*osarch = (*osarch)[strings.LastIndex(*osarch, ".")+1:]
 		v := strings.Split(*osarch, "-")
+		if len(v) == 3 {
+			v = v[:2] // support e.g. "linux-arm-scaleway" as GOOS=linux, GOARCH=arm
+		}
 		if len(v) != 2 || v[0] == "" || v[1] == "" {
 			log.Fatalf("invalid -osarch value %q", *osarch)
 		}