Merge pull request cli#3846 from cli/build-windows-fix

Improvements to build script on Windows

script/build.bat

@@ -0,0 +1 @@
+go run script\build.go %*

script/build.go

@@ -23,6 +23,7 @@
 package main
 
 import (
+	"errors"
 	"fmt"
 	"io/ioutil"
 	"os"
@@ -136,8 +137,14 @@ func date() string {
 
 func sourceFilesLaterThan(t time.Time) bool {
 	foundLater := false
-	_ = filepath.Walk(".", func(path string, info os.FileInfo, err error) error {
+	err := filepath.Walk(".", func(path string, info os.FileInfo, err error) error {
 		if err != nil {
+			// Ignore errors that occur when the project contains a symlink to a filesystem or volume that
+			// Windows doesn't have access to.
+			if path != "." && isAccessDenied(err) {
+				fmt.Fprintf(os.Stderr, "%s: %v\n", path, err)
+				return nil
+			}
 			return err
 		}
 		if foundLater {
@@ -151,6 +158,9 @@ func sourceFilesLaterThan(t time.Time) bool {
 			}
 		}
 		if info.IsDir() {
+			if name := filepath.Base(path); name == "vendor" || name == "node_modules" {
+				return filepath.SkipDir
+			}
 			return nil
 		}
 		if path == "go.mod" || path == "go.sum" || (strings.HasSuffix(path, ".go") && !strings.HasSuffix(path, "_test.go")) {
@@ -160,9 +170,18 @@ func sourceFilesLaterThan(t time.Time) bool {
 		}
 		return nil
 	})
+	if err != nil {
+		panic(err)
+	}
 	return foundLater
 }
 
+func isAccessDenied(err error) bool {
+	var pe *os.PathError
+	// we would use `syscall.ERROR_ACCESS_DENIED` if this script supported build tags
+	return errors.As(err, &pe) && strings.Contains(pe.Err.Error(), "Access is denied")
+}
+
 func rmrf(targets ...string) error {
 	args := append([]string{"rm", "-rf"}, targets...)
 	announce(args...)