cmd/go: on Windows, disable cache if LocalAppData is not set

Fixes #23146

Change-Id: I06e3328ecca5e27f8e1ada05c2d7cd9bdda714e6
Reviewed-on: https://go-review.googlesource.com/85996
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/go/internal/cache/default.go

@@ -68,6 +68,9 @@ func DefaultDir() string {
 	switch runtime.GOOS {
 	case "windows":
 		dir = os.Getenv("LocalAppData")
+		if dir == "" {
+			return "off"
+		}
 
 	case "darwin":
 		dir = os.Getenv("HOME")