runtime: skip TestGcSys on arm64

This failure occurs randomly on arm64.

13:10:32 --- FAIL: TestGcSys (0.06s)
13:10:32 gc_test.go:30: expected "OK\n", but got "using too much memory: 71401472 bytes\n"
13:10:32 FAIL

Updates #27636

Change-Id: Ifd4cfce167d8054dc6f037bd34368d63c7f68ed4
Reviewed-on: https://go-review.googlesource.com/135155
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/runtime/gc_test.go

@@ -24,6 +24,9 @@ func TestGcSys(t *testing.T) {
 	if runtime.GOOS == "windows" {
 		t.Skip("skipping test; GOOS=windows http://golang.org/issue/27156")
 	}
+	if runtime.GOOS == "linux" && runtime.GOARCH == "arm64" {
+		t.Skip("skipping test; GOOS=linux GOARCH=arm64 https://github.com/golang/go/issues/27636")
+	}
 	got := runTestProg(t, "testprog", "GCSys")
 	want := "OK\n"
 	if got != want {