RFR: Fix Minimal VM build

[Aleksey Shipilev]

On 06/06/2018 11:45 AM, Andrew Haley wrote:
> On 06/06/2018 10:43 AM, Aleksey Shipilev wrote:
>> On 06/06/2018 11:40 AM, Andrew Haley wrote:
>>> Why not just make it an unsupported configuration?
>>
>> Well, this is not Shenandoah issue, but build cleanness issue: once Shenandoah code lands in the
>> repo, all other build configurations should still be buildable, including minimal VM, zero, etc.
> 
> Got it.  So Shenandoah doesn't have to work with minimal VM, it just
> has to not break it.  OK.

Yup. Minimal wouldn't build any other GC except Serial, rendering Shenandoah unsupported automatically.

-Aleksey