cmd/go: send output of build and install to stderr

"go build" and "go install" were mixing stdout and stderr
from the toolchain, then putting it all on stdout. With this
change, it stays mixed, and is sent to stderr. Because
the toolchain does not create output in a clean compile/install,
sending all output to stderr makese more sense.

Also fix test.bash because of "mktemp: too few X's
in template `testgo'" on Linux.

Fixes #4917.

R=golang-dev, rsc, adg
CC=golang-dev
https://golang.org/cl/7393073

src/cmd/go/build.go

@@ -391,7 +391,9 @@ var (
 
 func (b *builder) init() {
 	var err error
-	b.print = fmt.Print
+	b.print = func(a ...interface{}) (int, error) {
+		return fmt.Fprint(os.Stderr, a...)
+	}
 	b.actionCache = make(map[cacheKey]*action)
 	b.mkdirCache = make(map[string]bool)
 
@@ -1632,7 +1634,7 @@ func (b *builder) libgcc(p *Package) (string, error) {
 		// print function to capture the command-line. This
 		// let's us assign it to $LIBGCC and produce a valid
 		// buildscript for cgo packages.
-		b.print = func(a ...interface{}) (n int, err error) {
+		b.print = func(a ...interface{}) (int, error) {
 			return fmt.Fprint(&buf, a...)
 		}
 	}

src/cmd/go/test.bash

@@ -11,18 +11,19 @@ ok=true
 unset GOPATH
 unset GOBIN
 
-# Test that error messages have file:line information
-# at beginning of line.
-for i in testdata/errmsg/*.go
-do
-	# TODO: |cat should not be necessary here but is.
-	./testgo test $i 2>&1 | cat >err.out || true
-	if ! grep -q "^$i:" err.out; then
-		echo "$i: missing file:line in error message"
-		cat err.out
-		ok=false
-	fi
-done
+# Test that error messages have file:line information at beginning of
+# the line. Also test issue 4917: that the error is on stderr.
+d=$(mktemp -d -t testgoXXX)
+fn=$d/err.go
+echo "package main" > $fn
+echo 'import "bar"' >> $fn
+./testgo run $fn 2>$d/err.out || true
+if ! grep -q "^$fn:" $d/err.out; then
+	echo "missing file:line in error message"
+	cat $d/err.out
+	ok=false
+fi
+rm -r $d
 
 # Test local (./) imports.
 testlocal() {
@@ -51,7 +52,7 @@ testlocal() {
 		ok=false
 	fi
 	
-	rm -f err.out hello.out hello
+	rm -f hello.out hello
 	
 	# Test that go install x.go fails.
 	if ./testgo install "testdata/$local/easy.go" >/dev/null 2>&1; then
@@ -183,7 +184,7 @@ fi
 
 # issue 4186. go get cannot be used to download packages to $GOROOT
 # Test that without GOPATH set, go get should fail
-d=$(mktemp -d -t testgo)
+d=$(mktemp -d -t testgoXXX)
 mkdir -p $d/src/pkg
 if GOPATH= GOROOT=$d ./testgo get -d code.google.com/p/go.codereview/cmd/hgpatch ; then 
 	echo 'go get code.google.com/p/go.codereview/cmd/hgpatch should not succeed with $GOPATH unset'
@@ -191,7 +192,7 @@ if GOPATH= GOROOT=$d ./testgo get -d code.google.com/p/go.codereview/cmd/hgpatch
 fi	
 rm -rf $d
 # Test that with GOPATH=$GOROOT, go get should fail
-d=$(mktemp -d -t testgo)
+d=$(mktemp -d -t testgoXXX)
 mkdir -p $d/src/pkg
 if GOPATH=$d GOROOT=$d ./testgo get -d code.google.com/p/go.codereview/cmd/hgpatch ; then
         echo 'go get code.google.com/p/go.codereview/cmd/hgpatch should not succeed with GOPATH=$GOROOT'
@@ -200,7 +201,7 @@ fi
 rm -rf $d
 
 # issue 3941: args with spaces
-d=$(mktemp -d -t testgo)
+d=$(mktemp -d -t testgoXXX)
 cat >$d/main.go<<EOF
 package main
 var extern string
@@ -226,7 +227,7 @@ rm -f strings.prof strings.test
 
 # issue 4568. test that symlinks don't screw things up too badly.
 old=$(pwd)
-d=$(mktemp -d -t testgo)
+d=$(mktemp -d -t testgoXXX)
 mkdir -p $d/src
 (
 	ln -s $d $d/src/dir1
@@ -247,7 +248,7 @@ fi
 rm -rf $d
 
 # issue 4515.
-d=$(mktemp -d -t testgo)
+d=$(mktemp -d -t testgoXXX)
 mkdir -p $d/src/example/a $d/src/example/b $d/bin
 cat >$d/src/example/a/main.go <<EOF
 package main
@@ -280,7 +281,7 @@ unset GOPATH
 rm -rf $d
 
 # issue 4773. case-insensitive collisions
-d=$(mktemp -d -t testgo)
+d=$(mktemp -d -t testgoXXX)
 export GOPATH=$d
 mkdir -p $d/src/example/a $d/src/example/b
 cat >$d/src/example/a/a.go <<EOF

src/cmd/go/testdata/errmsg/x.go

@@ -1,3 +0,0 @@
-package foo
-
-import "bar"

src/cmd/go/testdata/errmsg/x1_test.go

@@ -1,3 +0,0 @@
-package foo_test
-
-import "bar"

src/cmd/go/testdata/errmsg/x_test.go

@@ -1,3 +0,0 @@
-package foo
-
-import "bar"