[11] Review request: 8146672: [Windows] Support cmake ninja build

[Arunprasad Rajkumar]

Hi,

Please review the simple fix to enable ninja build generation from cmake on 
Windows. 

Linux and macOS builds are already supports ninja build.

JBS: https://bugs.openjdk.java.net/browse/JDK-8146672
Webrev: http://cr.openjdk.java.net/~arajkumar/8146672/webrev

Thanks,
Arun