os: check only user attributes in TestStatDirModeExec

Some have their system setup in a particular way,
see http://golang.org/issue/4444#c3.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/6851129

src/pkg/os/os_test.go

@@ -1098,12 +1098,22 @@ func TestLargeWriteToConsole(t *testing.T) {
 
 func TestStatDirModeExec(t *testing.T) {
 	const mode = 0111
-	const path = "."
+
+	path, err := ioutil.TempDir("", "go-build")
+	if err != nil {
+		t.Fatalf("Failed to create temp directory: %v", err)
+	}
+	defer RemoveAll(path)
+
+	if err := Chmod(path, 0777); err != nil {
+		t.Fatalf("Chmod %q 0777: %v", path, err)
+	}
+
 	dir, err := Stat(path)
 	if err != nil {
 		t.Fatalf("Stat %q (looking for mode %#o): %s", path, mode, err)
 	}
 	if dir.Mode()&mode != mode {
-		t.Errorf("Stat %q: mode %#o want %#o", path, dir.Mode(), mode)
+		t.Errorf("Stat %q: mode %#o want %#o", path, dir.Mode()&mode, mode)
 	}
 }