RFR: 8277517: Bump minimum boot jdk to JDK 18

[Mikael Vidstedt]

On Tue, 5 Apr 2022 03:19:06 GMT, Mikael Vidstedt <mikael at openjdk.org> wrote:

> With the JDK 18 GA out it's time to bump the minimum boot JDK version for mainline/JDK 19.
> 
> Testing: tier1-5, GHA builds

Adding a random comment here in the hopes that it will generate an email and give everybody a chance to react to this change.

-------------

PR: https://git.openjdk.java.net/jdk/pull/8102