runtime: skip GDB tests on Windows

Updates #22687.

Change-Id: Iedccd9d2416ae7150cd2febe81c8bc9493d8d65c
Reviewed-on: https://go-review.googlesource.com/112915
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/runtime/runtime-gdb_test.go

@@ -27,6 +27,8 @@ func checkGdbEnvironment(t *testing.T) {
 		t.Skip("gdb does not work on darwin")
 	case "netbsd":
 		t.Skip("gdb does not work with threads on NetBSD; see golang.org/issue/22893 and gnats.netbsd.org/52548")
+	case "windows":
+		t.Skip("gdb tests fail on Windows: https://golang.org/issue/22687")
 	case "linux":
 		if runtime.GOARCH == "ppc64" {
 			t.Skip("skipping gdb tests on linux/ppc64; see golang.org/issue/17366")