build: use go command during build

If something goes wrong, it should suffice to set
USE_GO_TOOL=false in env.bash to fall back to the
makefiles.  I will delete the makefiles in January.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5502047

src/buildscript.sh

+#!/bin/sh
+# Copyright 2011 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.
+
+. ./buildinfo.sh
+
+for sys in $GOOSARCHES
+do
+	export GOOS=$(echo $sys | sed 's/_.*//')
+	export GOARCH=$(echo $sys | sed 's/.*_//')
+	targ=buildscript_${GOOS}_$GOARCH.sh
+	rm -f $targ
+
+	(echo '#!/bin/bash
+# AUTO-GENERATED by buildscript.sh; DO NOT EDIT.
+# This script builds the go command (written in Go),
+# and then the go command can build the rest of the tree.
+
+export GOOS='$GOOS'
+export GOARCH='$GOARCH'
+export WORK=$(mktemp -d -t go-build)
+trap "rm -rf $WORK" EXIT SIGINT SIGTERM
+set -e
+
+'
+	go install -a -n cmd/go
+	)>$targ
+	chmod +x $targ
+done

src/env.bash

@@ -3,6 +3,10 @@
 # Use of this source code is governed by a BSD-style
 # license that can be found in the LICENSE file.
 
+# Set to false if something breaks, to revert back to Makefiles.
+# TODO: This variable will go away when the Makefiles do.
+USE_GO_TOOL=${USE_GO_TOOL:-true}
+
 # If set to a Windows-style path convert to an MSYS-Unix 
 # one using the built-in shell commands.   
 if [[ "$GOROOT" == *:* ]]; then

src/make.bash

@@ -85,10 +85,24 @@ do
 done
 
 echo; echo; echo %%%% making runtime generated files %%%%; echo
-(cd "$GOROOT"/src/pkg/runtime; ./autogen.sh) || exit 1
 
-echo; echo; echo %%%% making pkg %%%%; echo
-gomake -C pkg install
+(
+	cd "$GOROOT"/src/pkg/runtime
+	./autogen.sh
+	make install  # copy runtime.h to pkg directory
+) || exit 1
+
+if $USE_GO_TOOL; then
+	echo
+	echo '# Building go command from bootstrap script.'
+	./buildscript_${GOOS}_$GOARCH.sh
+
+	echo '# Building Go code.'
+	GOPATH="" go install -a all
+else
+	echo; echo; echo %%%% making pkg %%%%; echo
+	gomake -C pkg install
+fi
 
 # Print post-install messages.
 # Implemented as a function so that all.bash can repeat the output