RFR: JDK-8218177: Bump jib format_version to support new devkit archive layout

[Tim Bell]

Erik:

> With the new devkits I deployed recently (Oracle internal), the file
> layout changed as a top level directory inside the tar archive was
> introduced. This works in most cases, but there are certain situations
> where jib does not handle this well. This causes AOT testing on Linux to
> stop working with the run-test-prebuilt make target.
>
> This issue is being fixed in Jib, but to activate the fix a bump in the
> format_version is required. This patch does that, as well as adjusting
> to conform to the new behavior.
>
> Bug: https://bugs.openjdk.java.net/browse/JDK-8218177
>
> Webrev: http://cr.openjdk.java.net/~erikj/8218177/webrev.01/
>
> (note that the Jib fix is not yet live in production)

Looks good.

Tim