Revert "cmd/dist: support windows/arm"

This reverts commit def3280eb4.

Reason for revert: broke the vetall builder and I (Brad) forgot to run the trybots first. :(

Change-Id: I255bedeb28d13e265f357060e57561e593145275
Reviewed-on: https://go-review.googlesource.com/130015
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/cmd/dist/build.go

@@ -1422,7 +1422,6 @@ 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

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