RFR: JDK-8232133: Change to GCC 8.3 for building on Linux at Oracle

[Magnus Ihse Bursie]

> 10 okt. 2019 kl. 20:27 skrev Erik Joelsson <erik.joelsson at oracle.com>:
> 
> Updating defaults in devkit creator makefiles. Also remembering to update building.md this time.
> 
> Webrev: http://cr.openjdk.java.net/~erikj/8232133/webrev.01/

Looks good to me. 

/Magnus

> 
> Bug: https://bugs.openjdk.java.net/browse/JDK-8232133
> 
> /Erik
>