func OpenReader(name string) (*ReadCloser, error) {
	f, err := os.Open(name)
	if err != nil {
		return nil, err
	}
	fi, err := f.Stat()
	if err != nil {
		f.Close()
		return nil, err
	}
	r := new(ReadCloser)
	if err = r.init(f, fi.Size()); err != nil && err != ErrInsecurePath {
		f.Close()
		return nil, err
	}
	r.f = f
	return r, err
}

set -e

if [ ! -f run.bash ]; then
	echo 'clean.bash must be run from $GOROOT/src' 1>&2
	exit 1
fi
export GOROOT="$(cd .. && pwd)"

gobin="${GOROOT}"/bin
if ! "$gobin"/go help >/dev/null 2>&1; then
	echo 'cannot find go command; nothing to clean' >&2
	exit 1
fi

"$gobin/go" clean -i std
"$gobin/go" tool dist clean

# to see the available SDKs and replace iphoneos with one of them.
if [ "$GOARCH" == "arm64" ]; then
	SDK=iphoneos
	PLATFORM=ios
	CLANGARCH="arm64"
else
	SDK=iphonesimulator
	PLATFORM=ios-simulator
	CLANGARCH="x86_64"
fi

SDK_PATH=`xcrun --sdk $SDK --show-sdk-path`
export IPHONEOS_DEPLOYMENT_TARGET=5.1
# cmd/cgo doesn't support llvm-gcc-4.2, so we have to use clang.
CLANG=`xcrun --sdk $SDK --find clang`

// The downside is that renaming uname or gname by the OS never takes effect.
var userMap, groupMap sync.Map // map[int]string

func statUnix(fi fs.FileInfo, h *Header, doNameLookups bool) error {
	sys, ok := fi.Sys().(*syscall.Stat_t)
	if !ok {
		return nil
	}
	h.Uid = int(sys.Uid)
	h.Gid = int(sys.Gid)
	if doNameLookups {
		// Best effort at populating Uname and Gname.

	if err := os.Mkdir(dst, 0755); err != nil {
		return err
	}

	d, err := os.Open(src)
	if err != nil {
		return err
	}
	defer d.Close()
	fi, err := d.Readdir(-1)
	if err != nil {
		return err
	}

	for _, f := range fi {
		if f.IsDir() {
			if f.Name() == "testdata" {
				if err := cp(dst, filepath.Join(src, f.Name())); err != nil {
					return err
				}
			}
			continue

	}
	w.imported[name] = &importing

	// Determine package files.
	dir := w.importDir[name]
	if dir == "" {
		dir = filepath.Join(w.root, filepath.FromSlash(name))
	}
	if fi, err := os.Stat(dir); err != nil || !fi.IsDir() {
		log.Panicf("no source in tree for import %q (from import %s in %s): %v", name, fromPath, fromDir, err)
	}

	context := w.context
	if context == nil {
		context = &build.Default
	}