runtime: disable TestGdbAutotmpTypes in short mode on aix/ppc64

TestGdbAutotmpTypes takes more than one minute due to gdb performances.
Therefore, it must be skipped in short mode.

Change-Id: I253ebce62264cc7367c9b0f6ce9c5088a9994641
Reviewed-on: https://go-review.googlesource.com/c/go/+/164339Reviewed-by: Bryan C. Mills <bcmills@google.com>
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/runtime/runtime-gdb_test.go

@@ -36,8 +36,6 @@ func checkGdbEnvironment(t *testing.T) {
 		if runtime.GOARCH == "mips" {
 			t.Skip("skipping gdb tests on linux/mips; see https://golang.org/issue/25939")
 		}
-	case "aix":
-		t.Skip("gdb does not work on AIX; see https://golang.org/issue/28558")
 	case "freebsd":
 		t.Skip("skipping gdb tests on FreeBSD; see https://golang.org/issue/29508")
 	}
@@ -396,6 +394,10 @@ func TestGdbAutotmpTypes(t *testing.T) {
 	t.Parallel()
 	checkGdbVersion(t)
 
+	if runtime.GOOS == "aix" && testing.Short() {
+		t.Skip("TestGdbAutotmpTypes is too slow on aix/ppc64")
+	}
+
 	dir, err := ioutil.TempDir("", "go-build")
 	if err != nil {
 		t.Fatalf("failed to create temp directory: %v", err)