cmd/dist: support windows/arm

Updates #26148

Change-Id: I4744ebcc77fda3acc1301a1d8857754c0ee797fa
Reviewed-on: https://go-review.googlesource.com/130056
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/cmd/dist/build.go

@@ -1422,6 +1422,7 @@ var cgoEnabled = map[string]bool{
 	"solaris/amd64":   true,
 	"windows/386":     true,
 	"windows/amd64":   true,
+	"windows/arm":     false,
 }
 
 func needCC() bool {

src/cmd/dist/sys_windows.go

@@ -32,6 +32,7 @@ type systeminfo struct {
 const (
 	PROCESSOR_ARCHITECTURE_AMD64 = 9
 	PROCESSOR_ARCHITECTURE_INTEL = 0
+	PROCESSOR_ARCHITECTURE_ARM   = 5
 )
 
 var sysinfo systeminfo
@@ -43,6 +44,8 @@ func sysinit() {
 		gohostarch = "amd64"
 	case PROCESSOR_ARCHITECTURE_INTEL:
 		gohostarch = "386"
+	case PROCESSOR_ARCHITECTURE_ARM:
+		gohostarch = "arm"
 	default:
 		fatalf("unknown processor architecture")
 	}