Shenandoah critical native tests should only be ran on x86_64 platforms

[Roman Kennke]

Am 04.05.2018 um 18:35 schrieb Zhengyu Gu:
> Shenandoah critical native support is only implemented for x86_64, so
> only corresponding tests should only be ran on those platform.
> 
> Webrev:
> http://cr.openjdk.java.net/~zgu/shenandoah/critical-native-tests/webrev.00/
> 
> Test:
>   Two critical native tests on Linux x64
> 
> 
> Thanks,
> 
> -Zhengyu

Yes, please. Thanks!

Roman