RFR: 8006288: build-infra: Use solaris nm and not gnm on solaris

[Tim Bell]

Hi Erik:

Looks good... approved!

Tim

> Small patch changing configure to only look for nm and never gnm on 
> Solaris. Gnm is still needed in the compare script and is assigned to 
> a new variable GNM.
>
> http://cr.openjdk.java.net/~erikj/8006288/webrev.01/
>
> /Erik