[release-branch.go1.5] cmd/go: skip TestNoteReading2K on Windows

It's intended primarily as a torture test for OS X.
Apparently Windows can't take it.

Updates fix for #12327.

Change-Id: If2af249ea8e2f55bff8f232dce06172e6fef9f49
Reviewed-on: https://go-review.googlesource.com/17073Reviewed-by: Russ Cox <rsc@golang.org>
Reviewed-on: https://go-review.googlesource.com/17128Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/cmd/go/note_test.go

@@ -15,6 +15,9 @@ func TestNoteReading(t *testing.T) {
 }
 
 func TestNoteReading2K(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		t.Skipf("2kB is not enough on %s", runtime.GOOS)
+	}
 	// Set BuildIDReadSize to 2kB to exercise Mach-O parsing more strictly.
 	defer func(old int) {
 		main.BuildIDReadSize = old