misc/android: cleaner to remove stale GOROOT files

Updates #10806

Change-Id: I734d6db026cc7c2e3099a76dc8db8e42b2b90aa7
Reviewed-on: https://go-review.googlesource.com/10390Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

misc/android/cleaner.go

+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Cleaner removes anything from /data/local/tmp/goroot not on a builtin list.
+// Used by androidtest.bash.
+package main
+
+import (
+	"log"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+func main() {
+	const goroot = "/data/local/tmp/goroot"
+	expect := make(map[string]bool)
+	for _, f := range strings.Split(files, "\n") {
+		expect[filepath.Join(goroot, f)] = true
+	}
+
+	err := filepath.Walk(goroot, func(path string, info os.FileInfo, err error) error {
+		if expect[path] {
+			return nil
+		}
+		log.Printf("removing %s", path)
+		if err := os.RemoveAll(path); err != nil {
+			return err
+		}
+		if info.IsDir() {
+			return filepath.SkipDir
+		}
+		return nil
+	})
+	if err != nil {
+		log.Fatal(err)
+	}
+}