syscall: skip DirentRepeat test on freebsd

Dirent doesn't work properly. Diable the test for now.

Update #31416

Change-Id: I34a8045598a9c303dcc754ce04da3c124f122d1a
Reviewed-on: https://go-review.googlesource.com/c/go/+/171818Reviewed-by: Bryan C. Mills <bcmills@google.com>
Run-TryBot: Bryan C. Mills <bcmills@google.com>
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/syscall/dirent_bsd_test.go

@@ -87,6 +87,9 @@ func TestDirentRepeat(t *testing.T) {
 		if size < 1024 {
 			size = 1024 // DIRBLKSIZ, see issue 31403.
 		}
+		if runtime.GOOS == "freebsd" {
+			t.Skip("need to fix issue 31416 first")
+		}
 	}
 
 	// Make a directory containing N files