vendor: update buildkit

Signed-off-by: CrazyMax <crazy-max@users.noreply.github.com>

vendor/golang.org/x/tools/go/packages/visit.go

@@ -0,0 +1,59 @@
+// Copyright 2018 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.
+
+package packages
+
+import (
+	"fmt"
+	"os"
+	"sort"
+)
+
+// Visit visits all the packages in the import graph whose roots are
+// pkgs, calling the optional pre function the first time each package
+// is encountered (preorder), and the optional post function after a
+// package's dependencies have been visited (postorder).
+// The boolean result of pre(pkg) determines whether
+// the imports of package pkg are visited.
+func Visit(pkgs []*Package, pre func(*Package) bool, post func(*Package)) {
+	seen := make(map[*Package]bool)
+	var visit func(*Package)
+	visit = func(pkg *Package) {
+		if !seen[pkg] {
+			seen[pkg] = true
+
+			if pre == nil || pre(pkg) {
+				paths := make([]string, 0, len(pkg.Imports))
+				for path := range pkg.Imports {
+					paths = append(paths, path)
+				}
+				sort.Strings(paths) // Imports is a map, this makes visit stable
+				for _, path := range paths {
+					visit(pkg.Imports[path])
+				}
+			}
+
+			if post != nil {
+				post(pkg)
+			}
+		}
+	}
+	for _, pkg := range pkgs {
+		visit(pkg)
+	}
+}
+
+// PrintErrors prints to os.Stderr the accumulated errors of all
+// packages in the import graph rooted at pkgs, dependencies first.
+// PrintErrors returns the number of errors printed.
+func PrintErrors(pkgs []*Package) int {
+	var n int
+	Visit(pkgs, nil, func(pkg *Package) {
+		for _, err := range pkg.Errors {
+			fmt.Fprintln(os.Stderr, err)
+			n++
+		}
+	})
+	return n
+}