spec/ruby/core/process/spawn_spec.rb: skip a test on Android
spec/ruby/core/process/spawn_spec.rb: skip a test on Android

On Android, STDERR seems to be open even its invoker closes it.

http://rubyci.s3.amazonaws.com/android29-x86_64/ruby-master/log/20201001T014315Z.fail.html.gz

```
1)
Process.spawn closes STDERR in the child if :err => :close FAILED
Expected (59840): "out\nrescued\n"
         but got: "out\n"
```

ruby/spec,nobu/rubyspec,ruby/spec,nobu/rubyspec,nobu/rubyspec,ruby/spec