[dev.cc] cmd/dist: bootstrap Go toolchain using Go 1.4

Bootstrap the Go parts of the Go toolchain using Go 1.4,
as described in https://golang.org/s/go15bootstrap.

The first Go part of the Go toolchain will be cmd/objwriter,
but for now that's just an empty program to test that this
new code works.

Once the build dashboard is okay with this change,
we'll make objwriter a real program depended upon by the build.

Change-Id: Iad3dce675571cbdb5ab6298fe6f98f53ede47d5c
Reviewed-on: https://go-review.googlesource.com/3044
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/cmd/dist/util.go

@@ -275,7 +275,7 @@ func xremoveall(p string) {
 	os.RemoveAll(p)
 }
 
-// xreaddir replaces dst with a list of the names of the files in dir.
+// xreaddir replaces dst with a list of the names of the files and subdirectories in dir.
 // The names are relative to dir; they are not full paths.
 func xreaddir(dir string) []string {
 	f, err := os.Open(dir)
@@ -290,6 +290,27 @@ func xreaddir(dir string) []string {
 	return names
 }
 
+// xreaddir replaces dst with a list of the names of the files in dir.
+// The names are relative to dir; they are not full paths.
+func xreaddirfiles(dir string) []string {
+	f, err := os.Open(dir)
+	if err != nil {
+		fatal("%v", err)
+	}
+	defer f.Close()
+	infos, err := f.Readdir(-1)
+	if err != nil {
+		fatal("reading %s: %v", dir, err)
+	}
+	var names []string
+	for _, fi := range infos {
+		if !fi.IsDir() {
+			names = append(names, fi.Name())
+		}
+	}
+	return names
+}
+
 // xworkdir creates a new temporary directory to hold object files
 // and returns the name of that directory.
 func xworkdir() string {
@@ -370,6 +391,8 @@ func main() {
 		if gohostarch == "" {
 			fatal("$objtype is unset")
 		}
+	case "windows":
+		exe = ".exe"
 	}
 
 	sysinit()