os: cleanup directories created by TestLongPath

Add tmpdir as a parameter to the closure otherwise the subsequent
modifications to tmpdir causes only the last subdirectory to be
removed.

Additionally, add the missing argument for the t.Fatalf call.

Change-Id: I3df53f9051f7ea40cf3f846d47d9cefe445e9b9d
Reviewed-on: https://go-review.googlesource.com/32892Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/os/os_test.go

@@ -1703,11 +1703,11 @@ func TestReadAtEOF(t *testing.T) {
 
 func TestLongPath(t *testing.T) {
 	tmpdir := newDir("TestLongPath", t)
-	defer func() {
-		if err := RemoveAll(tmpdir); err != nil {
+	defer func(d string) {
+		if err := RemoveAll(d); err != nil {
 			t.Fatalf("RemoveAll failed: %v", err)
 		}
-	}()
+	}(tmpdir)
 	for len(tmpdir) < 400 {
 		tmpdir += "/dir3456789"
 	}
@@ -1751,7 +1751,7 @@ func TestLongPath(t *testing.T) {
 			}
 		}
 		if err := Truncate(tmpdir+"/bar.txt", 0); err != nil {
-			t.Fatalf("Truncate failed: %v")
+			t.Fatalf("Truncate failed: %v", err)
 		}
 	}
 }