RFR: 8252114: Windows-AArch64: Enable and test ZGC and ShenandoahGC [v2]

[Aleksey Shipilev]

On Fri, 11 Sep 2020 06:21:46 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> Monica Beckwith has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   x$OPENJDK_TARGET_CPU" = "xaarch64"
>>   
>>   Incorporating Aleksey's comments to incorporate 'x'
>
> The check looks fine now.

> Ref: [#97 (comment)](https://github.com/openjdk/jdk/pull/97#issuecomment-690811308)
> Now coming back to this - @stooart-mon, do you think it is OK to just check for aarch64 (similar to Shenandoah)?
> @stefank what do you think of simplifying the x86 checks (similar to Shenandoah)? Thanks all.

I believe keeping OS-specific checks for ZGC is better, as it reflects the reality of needing the OS-specific code
there. We don't want to try and build on OS we know ZGC does not support (yet). Shenandoah does not have OS-specific
code, only the arch-specific one, and so can live with OS checks only.

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PR: https://git.openjdk.java.net/jdk/pull/97