[8u] RFR: JDK-8139813: Base heap size on type of boot jdk, not architecture of build machine

[Tim Bell]

Hi Erik:

> Please review this minor configure fix. The logic in configure for 
> setting up proper mx flags for the bootjdk is flawed in that it 
> assumes a 64bit bootjdk if the build machine is 64bit. This patch 
> fixes this by instead testing if the bootjdk is 64bit or not. The 
> problem was discovered in 8u and is causing trouble for certain build 
> setups there. Since it also applies to 9, I'm posting a webrev for 
> each, intending to fix this in both releases.
>
> Bug: https://bugs.openjdk.java.net/browse/JDK-8139813
> Webrev JDK 9: http://cr.openjdk.java.net/~erikj/8139813/webrev.jdk9.01/
> Webrev JDK 8u: http://cr.openjdk.java.net/~erikj/8139813/webrev.jdk8u.01/

Looks good to me.

Tim