RFR: JDK-8221414: Bump required boot jdk version to 12

[Mikael Vidstedt]

Looks good.

Cheers,
Mikael

> On Mar 25, 2019, at 3:44 PM, Erik Joelsson <erik.joelsson at oracle.com> wrote:
> 
> With the release of JDK 12 it is now time to update the required boot jdk version for JDK 13 (to 12). This patch changes the configure requirements as well as bumps the version used for Jib builds at Oracle.
> 
> Bug: https://bugs.openjdk.java.net/browse/JDK-8221414
> 
> Webrev: http://cr.openjdk.java.net/~erikj/8221414/webrev.01/
> 
> /Erik
>