cmd/dist, cmd/go, misc/cgo/testshared: update testshared and run it on arm

And enable PIE in cmd/go because that's all it seems to take.

Change-Id: Ie017f427ace5e91de333a9f7cba9684c4641dfd5
Reviewed-on: https://go-review.googlesource.com/14222Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Michael Hudson-Doyle <michael.hudson@canonical.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

misc/cgo/testshared/shared_test.go

@@ -21,6 +21,7 @@ import (
 	"os/exec"
 	"path/filepath"
 	"regexp"
+	"runtime"
 	"strings"
 	"testing"
 	"time"
@@ -203,11 +204,14 @@ func TestNoTextrel(t *testing.T) {
 }
 
 // The install command should have created a "shlibname" file for the
-// listed packages (and runtime/cgo) indicating the name of the shared
-// library containing it.
+// listed packages (and runtime/cgo, and math on arm) indicating the
+// name of the shared library containing it.
 func TestShlibnameFiles(t *testing.T) {
 	pkgs := append([]string{}, minpkgs...)
 	pkgs = append(pkgs, "runtime/cgo")
+	if runtime.GOARCH == "arm" {
+		pkgs = append(pkgs, "math")
+	}
 	for _, pkg := range pkgs {
 		shlibnamefile := filepath.Join(gorootInstallDir, pkg+".shlibname")
 		contentsb, err := ioutil.ReadFile(shlibnamefile)

src/cmd/dist/test.go

@@ -587,7 +587,7 @@ func (t *tester) supportedBuildmode(mode string) bool {
 		return false
 	case "shared":
 		switch pair {
-		case "linux-amd64":
+		case "linux-amd64", "linux-arm":
 			return true
 		}
 		return false

src/cmd/go/build.go

@@ -378,7 +378,7 @@ func buildModeInit() {
 			fatalf("-buildmode=pie not supported by gccgo")
 		} else {
 			switch platform {
-			case "android/arm", "linux/amd64", "android/amd64", "linux/ppc64le":
+			case "linux/arm", "android/arm", "linux/amd64", "android/amd64", "linux/ppc64le":
 				codegenArg = "-shared"
 			default:
 				fatalf("-buildmode=pie not supported on %s\n", platform)