build/env: add Dockerfile for cross-compiling from x86 to arm

Moved cross-compile builders to env/crosscompile

Tested it works:

$ readelf --headers go/bin/go
ELF Header:
  Magic:   7f 45 4c 46 01 01 01 00 00 00 00 00 00 00 00 00
  Class:                             ELF32
  Data:                              2's complement, little endian
  Version:                           1 (current)
  OS/ABI:                            UNIX - System V
  ABI Version:                       0
  Type:                              EXEC (Executable file)
  Machine:                           ARM
  Version:                           0x1
  Entry point address:               0xc3a80
  Start of program headers:          52 (bytes into file)
  Start of section headers:          276 (bytes into file)
  Flags:                             0x5000002, has entry point, Version5 EABI
  Size of this header:               52 (bytes)
  Size of program headers:           32 (bytes)
  Number of program headers:         7
  Size of section headers:           40 (bytes)
  Number of section headers:         23
  Section header string table index: 7

Change-Id: I3db71fa954575c29bb0a12a07c9bf84c4c96d88e
Reviewed-on: https://go-review.googlesource.com/29679
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

env/crosscompile/linux-arm-stretch/Dockerfile

@@ -0,0 +1,51 @@
+# Copyright 2016 The Go Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style
+# license that can be found in the LICENSE file.
+
+# Linux builder VM running Debian stretch (i.e. Debian testing)
+# Docker tag gobuilders/linux-armel-stretch
+
+FROM debian:stretch
+MAINTAINER golang-dev <golang-dev@googlegroups.com>
+
+ENV DEBIAN_FRONTEND noninteractive
+
+# curl: for getting and unpacking Go 1.4 source
+# git-core: for interacting with the Go source & subrepos
+# gcc, libc-dev: for building Go's bootstrap 'dist' prog
+# gcc-armel-linux-gnu, libc6-dev-armel-cross: for armel builds
+# procps, lsof, psmisc: misc tools
+RUN apt-get update && apt-get install -y \
+	bzip2 \
+	ca-certificates \
+	curl \
+	git-core \
+	gcc \
+	libc6-dev \
+	gcc-arm-linux-gnueabi \
+	libc6-dev-armel-cross \
+	procps \
+	lsof \
+	psmisc \
+	--no-install-recommends \
+	&& rm -rf /var/lib/apt/lists/*
+
+RUN mkdir -p /go1.4-amd64 \
+	&& ( \
+		curl --silent https://storage.googleapis.com/golang/go1.4.3.linux-amd64.tar.gz | tar -C /go1.4-amd64 -zxv \
+	) \
+	&& mv /go1.4-amd64/go /go1.4 \
+	&& rm -rf /go1.4-amd64 \
+	&& rm -rf /go1.4/pkg/linux_amd64_race \
+		/go1.4/api \
+		/go1.4/blog \
+		/go1.4/doc \
+		/go1.4/misc \
+		/go1.4/test \
+	&& find /go1.4 -type d -name testdata | xargs rm -rf
+
+RUN curl -o /usr/local/bin/stage0 https://storage.googleapis.com/go-builder-data/buildlet-stage0.linux-amd64-kube \
+	&& chmod +x /usr/local/bin/stage0
+
+ENV GOROOT_BOOTSTRAP=/go1.4 GOOS=linux GOARCH=arm CC_FOR_TARGET=arm-linux-gnueabi-gcc
+COPY build-release.sh /usr/bin/

env/crosscompile/linux-arm-stretch/README

@@ -0,0 +1,2 @@
+The docker image created from this directory can be used to cross compile go
+from linux/amd64 to linux/arm.

env/crosscompile/linux-s390x-stretch/Makefile

@@ -0,0 +1,25 @@
+# Copyright 2016 The Go Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style
+# license that can be found in the LICENSE file.
+
+IMAGE_NAME=$(shell basename $(CURDIR))
+STAGING_REPO=gcr.io/go-dashboard-dev
+PROD_REPO=gcr.io/symbolic-datum-552
+
+usage:
+	echo "Use staging, prod, or dev targets. For dev, specify your Docker repository with the REPO=foo argument." ; exit 1
+
+staging: Dockerfile
+	docker build -t $(STAGING_REPO)/$(IMAGE_NAME):latest .
+	gcloud docker push $(STAGING_REPO)/$(IMAGE_NAME):latest
+
+prod: Dockerfile
+	docker build -t $(PROD_REPO)/$(IMAGE_NAME):latest .
+	gcloud docker push $(PROD_REPO)/$(IMAGE_NAME):latest
+
+# You must provide a REPO=your-repo-name arg when you make
+# this targarget. REPO is the name of the Docker repository
+# that will be prefixed to the name of the image being built.
+dev: Dockerfile
+	docker build -t $(REPO)/$(IMAGE_NAME):latest .
+	gcloud docker push $(REPO)/$(IMAGE_NAME):latest

env/crosscompile/linux-s390x-stretch/README

@@ -0,0 +1,2 @@
+The docker image created from this directory can be used to cross compile go
+from linux/amd64 to linux/s390x.

env/linux-s390x-stretch/README

@@ -1,10 +0,0 @@
-The docker image created from this directory can be used to cross compile go
-from linux/amd64 to linux/s390x.
-
-How to use:
-
-$ docker run --rm -it -v $(pwd)/artifacts:/artifacts \
-    gobuilders/linux-s390x-stretch build-release.sh $GIT_REV
-
-This will make the built go artifact, go-${GIT_REV}-linux-s390x.tar.gz,
-available in the directory you mounted as `/artifacts` in the container.

env/linux-s390x-stretch/build-release.sh

@@ -1,28 +0,0 @@
-#!/bin/bash
-# Copyright 2016 The Go Authors. All rights reserved.
-# Use of this source code is governed by a BSD-style
-# license that can be found in the LICENSE file.
-set -e
-
-GIT_REV=$1
-if [[ -z "$GIT_REV" ]]; then
-	GIT_REV=master
-fi
-
-# fetch the source
-git clone https://go.googlesource.com/go /usr/src/go
-(
-cd /usr/src/go
-# checkout the specific revision
-git checkout "$GIT_REV"
-
-cd /usr/src/go/src
-# build
-./bootstrap.bash
-
-cd /
-mv /usr/src/go-${GOOS}-${GOARCH}-bootstrap /go
-mkdir -p /artifacts
-# tarball the artifact
-tar -czvf /artifacts/go-${GIT_REV}-${GOOS}-${GOARCH}.tar.gz /go
-)