runtime/pprof: disable TestMorestack on darwin/arm64

Something is weird about darwin and TestMorestack,
but it is only manifesting on arm64 and race+amd64.
Disable for now.

Change-Id: I5862372fdd0b5ffae802fdefb65b2aa04e266fcc
Reviewed-on: https://go-review.googlesource.com/c/go/+/294409
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>

src/runtime/pprof/pprof_test.go

@@ -591,6 +591,11 @@ func TestMorestack(t *testing.T) {
 		// https://build.golang.org/log/280d387327806e17c8aabeb38b9503dbbd942ed1
 		t.Skip("skipping on darwin race detector")
 	}
+	if runtime.GOOS == "darwin" && runtime.GOARCH == "arm64" {
+		// For whatever reason, darwin/arm64 also doesn't work.
+		// https://build.golang.org/log/c45e82cc25f152642e6fb90d882ef5a8cd130ce5
+		t.Skip("skipping on darwin/arm64")
+	}
 	testCPUProfile(t, stackContainsAll, []string{"runtime.newstack,runtime/pprof.growstack"}, avoidFunctions(), func(duration time.Duration) {
 		t := time.After(duration)
 		c := make(chan bool)